:SugarwareZ-229: Syllabus
Introduction to Computer Terminology
Centralised Data processing system
Types of hardware configuration, peripherals etc.
Systems Software:
DOS, NOVELL, UNIX
Operating system functions
Translators
Compilers
Interpreters
Application Software
Programming Languages and their characteristics
Foxpro
C
Introduction to
Electronic Spread Sheet
Data Base Management Systems
Word Processors
Graphic User Interfaces
Introduction to Foxpro
Writing simple programs
Introduction to Relational Data Base
CONTENTS
Evaluation of Computers
Numbering System
Computer and Devices
Operating System/ Interpreter/ Compiler
Languages
System Development Life Cycle
Networking
Network Design
Network Communication Media
Network Connecting Devices
Models of File Management System
Models of Database Management System
Advantages of DBMS over File Management System
Management Information System
Internet
WEB
EVALUATION OF COMPUTERS
First generation computers (1957 - 58)
They were large, not reliable and use of vacuum tubes
1) Tremendous heat caused more failures.
2) Punched cards were used to feed data and instructions.
3) Instructions were coded in binary system, which was cumbersome. And time consuming.
4) Assembler was used to translate Assembly language program in binary language required
5) Chore space proer and heat generation high second generation Computer ( 1959 – 1964)
Second Generation Computers (1959-64)
Vacuum tubes were replaced with Transistors. This resulted in
1) Less heat generation, lesser space and power required.
2) More reliable and faster processing.
3) Higher Storage capacity.
4) Punch card used.
5) Magnetic tape were used as Storage media
6) Programming techniques were refined resulting in new high level languages like Fortran Cobol
Third generation Computer (1965 – 1971)
Transistors were replaced by Integrated Circuits (IC) Which consisted of hundreds of electronic components, put on a Silicon Chip.
1) Smaller Size of Computer
2) Cheaper Computers
3) Lesser power required
4) Faster Processing
5) More reliability
IBM first introduced with system 360 series. This technology change introduced concept of mini Computers and remote terminal. Remote Terminals allowed processing from distant locations by connecting terminals to center computer and using its capabilities. This concept was known as time-sharing and many users were able to run separate programs simultaneously.
Forth generation Computers (1972 – till sate)
IC were further integrated calling it large scale Integration
(LSI) which is also called Microchip, which further helped in development of Microprocessor.
With Lesser Cost of Computer its usage increased at home, education and business.
Fifth generation Computers (Future)
This is in development stage to build intelligent computer, which will be able to converse with humans in natural language. Computer will be able to take decisions on learned experience (Attificial Intelligence) and memory capabilities
Computer will be able to learn, make inferences, and make decisions.
NUMBERING SYSTEM
We have seen that computer can understand two characters namely “0” and “1”.
Each of this is called BIT, abbreviation for Binary Digit.
A set of letters A to Z, a to z, punctuation, 32 control character, 129 special character, totaling 256 character is called Alphanumeric Character Set.
Consider a number 4568
Each digit is determined by
The digit itself
The position of the digit in number
The base of the number itself
Base is the number of distinct symbols used in that system.
Example: In decimal system there are ten symbols as 0,1,2,3,4,5,6,7,8,9, so it’s base is 10.
In Binary system there are two symbols namely 0 and 1 so the base is 2.
Since 2 bits is not sufficient for representing these 256 character set, a set of 8 digits is considered and this combination of 8 digits is called BYTE.
2 raised to power 8 = 2x2x2x2x2x2x2x2 = 256
Like us, computer expresses information in WORDS. A combination of bits is called a WORD. The length of a Word will vary from computer to computer. Word length determines the information OR number of bits CPU moves internally or externally.
For convenience data whether in memory or hard disk, is measured in bytes or higher denominations of byte
1024 bytes = Kilobyte (Kb)
10,48,576 bytes = Megabyte (Mb)
107,37,41,824 bytes = Gigabyte (Gb)
* We are familiar with a system where we have number 0 to 9. This is called Decimal system.
We have also seen the computer can understand only 0 and 1.
* Representation of character by 0 and 1 is called Binary System.
• Initially, combinations of 6 bits were considered for representation of a character. This is called Binary Coded Decimal System.
To increase the representation of number of characters the length was increased from 6 to 8. However this time two thoughts prevailed for representation, namely ASCII and EBCDIC.
* ASCII – American National Standard Code.
For Information Interchange.
This system uses 7 bits for a byte. 2 raise to 7 = 128 character representation.
* EBCDIC – Extended Binary Coded Decimal Interchange Code.
This system uses 8 bits for a byte, 2 raise to 8 = 256 character representation.
Take an example:
Decimal number Binary number
0 00
1 01
2 10
3 11
4 100
5 101
6 110
7 111
8 1000
9 1001
In above we see that
We require 2 bits to represent decimal numbers 0 to 3
We require 3 bits to represent decimal numbers 4 to 7
We require 4 bits to represent decimal numbers 8 and 9
That means each decimal number representation in binary requires on average 3.2 bits.
In ASCII we have seen we use 7 bits. The eight bit is used for error checking what is called parity check. Computers have either odd or even bit parity checks. After conversion from decimal to binary if total 1 is even and computer is odd bit parity check then 1 is added at right most level to make it odd parity check.
We have seen that a decimal digit takes 3.2 bits in binary form. Thus 10 digits of decimal will take about 32 bits of binary form. It will be difficult to write such long strings of 1 and 0 and chances of error will be more. So IBM devised EBCDIC system where 16 is used a base viz. 0,1,2,3,4,5,6,7,8,9,A, B, C, D, E, and F.
CONVERSION FROM DECIMAL TO BINARY
Consider a decimal number 25. This will be expressed in decimal form as (25) base 10. If this is to be converted in binary with base 2, the conversion will be as under:
1 Divide the number by base that is 2
2 Write down the remainder
Repeat step 1 & 2 till quotient is zero
2 |25 1
2 |12 0
2 |6 0
2 |3 1
2 |1 1
(1x2) + (1x2) + (0x2) + (0x2) + 1x2)
QUESTIONS
1 Convert decimal 36 in binary
2 Convert decimal 2345 in binary
CONVERSION FROM DECIMAL TO HEXADECIMAL
Consider a decimal number 25. This will be expressed in decimal form as (25) base 10. if this is to be converted in hexadecimal with base 16, the conversion will be as under:
1. Divide the number by base that is 16
2. Write down the remainder
Repeat step 1 & 2 till quotient is zero
16 |25 9
16 |1 1
|0
(1x16) + (9x16)
16+9 = 25
QUESTIONS
1 convert decimal 36 in binary
2 convert decimal 2345 in binary.
CONVERSION FROM DECIMAL FRACTIONS TO BINARY
The decimal fraction is expressed as sum of negative power of 2.
STEPS
1 Multiply a decimal fraction by 2
2 The integer part will be most significant bit of the binary fraction
3 The fractional part of the answer is multiplied by 2 to obtain the next significant bit of the binary fraction.
4 The procedure is continued till the fractional part is zero.
EXAMPLE
1 Find binary equivalent of 0.7
0.70 x 2 = 1.40 1 most significant bit
0.40 x 2 = 0.80 0
0.80 x 2 = 1.60 1
0.60 x 2 = 1.20 1
0.20 x 2 = 0.40 0
----------------------------
0.40 x 2 = 0.80 0 recurs beyond this point
Thus (0.7) base 10 = (0.B3) (3) base 16
2 Find binary equivalent of 0.5625
0.5625 x 2 = 1.125 1 most significant bit
0.125 x 2 = 0.250 0
0.250 x 2 = 0.500 0
0.500 x 2 = 1.000 1
(0.5625) base 10 = (0.1001) base 2
CONVERSION OF DECIMAL FRACTION IN HEXADECIMAL FRACTIONS
1 Multiply a decimal fraction by base 16
2 The integer part will be most significant bit of the binary fraction
3 The fractional part of the answer is multiplied by 16 to obtain the next the next significant bit of the binary fraction
4 The procedure is continued till the fractional part is zero
EXAMPLE
1 Find binary equivalent of 0.7
0.70 x 16 = 11.20 11 most significant bit
0.20 x 16 = 03.20 3
---------------------------------------------
0.20 x 16 = 3.20 3 recurs beyond this point
Thus (0.7) base 10 = (0.B3) (3) base 16
2 Find binary equivalent of 0.5625
0.5625 x 16 = 9.0000 9 most significant bit
(0.5625) base 10 = (0.9) base 16
COMPUTER AND DEVICES
Having in general talked about computer, let us see technically how a computer can be described.
A computer can be thought as a machine that would carry out instructions obediently, uncritically with high speed and without emotions.
As human being, we use emotions which is called commonsense but computers does not have judgement and commonsense.
Example: A colonel sent his order to post office with order
“ Go to post office and buy ten number of 25 paisa stamp”
Orderly went to post office and did not return for a long period. Colonel went in search of him to post office and found orderly standing there with stamps in his hand. When colonel asked him, pet came the reply that he was ordered to buy ten 25-paisa stamps but not ordered to return with them.
Computer does not understand commonsense and will stop functioning in such cases, which is called hanging of the system.
ALGORITHM: is a finite sequence of instructions to solve a problem and has following basics:
Acceptance of input
Processing rules, which are unambiguous and can be carried out
Each instruction must be sufficiently basic
Time to carry out instructions must be finite.
Must produce output.
It has been derived from “al-khowarizmi” an Arabic mathematician “Abu Jafar Mohammed ibn Musa al-khowarizmi”. Father of Jafar, son of Musa and resident of al-khowarizmi.
We have seen that the computer system consists of three segments
Input
Hardware devices from which information is received
Central processing
Hardware, which does processing of information
Output
Hardware devices, which help in producing results of processing by central processing.
INPUT DEVICES
Punch card
This is a thin card of 18.8 cm x 8.3 cm size. It is divided into 80 columns and 12 rows. Rows are numbered A, B and 0 to 9 starting from top to down. Combination of holes in rows of each column occupies a character.
Keyboard
There are alfa keys, Numeric keys, special character keys, and some functional keys.
INPUT/OUTPUT DEVICES
Floppy
It is a flexible magnetic coated plastic of 5 ¼” diameter.
When power is turned on, a small motor rotates the floppy drive under a magnetic head.
It is of sizes 8”, 5 ¼”, 3 ½” and capacity 128 KB, 256 KB, 768 KB, 1.44 MB
Floppy can be Hard sector/ Soft sector floppies.
In hard sector floppy, sides to be used, location & number of tracks, are set by hardware characteristics of floppy and the floppy drive. This cannot be changed.
In soft sector floppy, location, size and number of sectors within a track are defined by software. A sector may have 128/256/512/1024 characters. This is done when the floppy is being formatted.
HARD DISK
It can be conceived of having many floppies put together. Disk operations are controlled by “Disk Controller”. Hard disk can have multiple platters each having two sides. The portion occupied by the same track in all platters, together is called a cylinder.
Number of read/write heads will depend on number of platters in a disk.
Formatting a floppy or disk, divides the sectors into four sections.
BOOT RECORD :
It contains a shore program to start the process of loading of operating system. . Other Information on this will vary on type of format being used.
File Allocation Table:
FAT follows boot record and contains information on how disk has been formatted and also the Map of location of sectors used by data files.
It keeps information of each file, its name, size and start sector.
DATA SPACE
Remaining sectors occupies the data. Data is kept in the form of cluster which in a floppy. Number of sectors in a cluster will vary from type of diskette being used. In one-sided floppy, it is one sector and in double sided floppy, it is a pair of adjacent sectors.
FIXED / REMOVABLE DISK
Now a days all disks are fixed. Previously on mainframe there used to be disks, which can be removed and inserted. In today’s context, we have concept “ Hot swappable disk” which means that when computer is working disks can be removed and new disks can be inserted.
COMPACT DISK
OUTPUT DEVICES
MONITOR
Called VDU, where information is displayed, either through keyboard or from CPU.
PRINTERS
Printers are of types, namely serial and line printers Inkjet and Laser.
Dot matrix
Line dot matrix
Daisy Wheel
Drum
Chain
Inkjet
Laser
Serial printers take one character at a time with printer head moving across the line. Characters are sent from memory to printer, decoded by printer electronics and printed by activating pins.
Line printers print aline at a time. These are also called parallel printers.
Each printer has a logic card for conversion of signals in to characters and also a memory, which is called a buffer memory.
Inkjet Printers
Laser Printers
CENTRAL PROCESSING UNIT
Processor
This is the main, which controls the operations of compute system. This microprocessor delegates certain control functions to other chips and CPU in free to attend to its own work. These are called device controllers and housed on different slots of motherboard. To name a few, for example:
Interrupt Controller
Direct Memory Access Controller (DMA)
Clock Generator
CRT Controller
Disk controller
Diskette controller
Arithmetic Logic Unit
All these controllers along with CPU are fixed on a board and connected through a circuitry, which is called the motherboard.
The main circuitry to which different circuits are connected is called a bus. There are mainly two types of bus, namely Address and Data.
Address bus transmits the addresses of memory cells and devices.
Data bus in conjunction with address bus carry data throughout computer
MEMORY
Memory is made up of large number of cells, each cell capable of storing one bit. Cells may be organized as set of addressable words. In such a situation if time to store and retrieve a word is independent of the address of the word than it is called Random Access Memory. This is main memory of the computer. Presently these are made of semiconductor.
If the memory cell information is permanently written than it is called Read Only Memory.
Different type of RAM is
SRAM; Static Random Access Memory
DRAM; Dynamic Random Access Memory
Virtual / Secondary Memory is the device on which additional information is written. Information is brought to and from this device. It can be hard disk, Tape, CD, and Floppy.
Cache memory is a part of memory controlled by cache controller, which stores the contents of frequently accessed memory locations and their addresses.
OPERATING SYSTEM
Software can be classified as Systems software and Application software.
An operating System, which can be classified as part of systems software, is a series of programs used by the computer to manage its operations as well as allow the users to interact with the computer through various devices.
It is a set of programs that acts as middle layer between application software and computer hardware. Computers with different hardware architecture will have different operating systems.
When the computer is turned on, it is the first program, which is loaded in computer memory and will remain in memory till the computer is turned off.
Operating Systems are developed in two ways:
OS developed with software in mind and Networking features are added later on. This is susceptible to bugs. Example: Microsoft Windows.
OS developed with Networking in mind and software features are added later on. These are robust OS. Example: UNIX, NETWARE
Major functions of Operating systems are
Memory Management
Space/Disk management
Input / Output devices management.
TYPES of Operating System
Single User
This means that one person can work at a time and only one job can be executed at a particular time.
Best example is of PC working under DOS (Disk Operating System) and the user working on a “Spread Sheet” or “MS-Office.”
Example: Dos, WINDOWS 95/98
Multitasking Operating System
This type of operating system allows a user to process more than on job at a time. Monitor screen can be split into a number of sections (windows) each one running a separate job. One window may be running a spreadsheet while other may be on MS- office.
Example: UNIX
Multi-user Operating System.
This allows a number of users to share a single computer connected to each user PC. Each user is able to share the same operating system and files of the main computer.
Example: WINDOWS NT, Novell Netware
INTERPRETER
Interpreter is a software program, which reads one line of a program, changes it into machine code and then executes it. This procedure is followed with each line of that program till that program is executed fully.
If this program is to be run again, the interpreter has to go through the same procedure again.
This method is slow and takes more storage space. However it has the advantage that it can be interrupted during execution, changed if there are mistakes and then restarted. Because of this reason this is used for testing/debugging of programs.
COMPLIERS
This software program to create machine code from a source program. This process is called compilation. Programs written in Languages cannot run unless they are compiled first.
The program generated after compilation called executable, in run on computer to process the job. This is faster operation as interpretation stage is eliminated.
LANGUAGES
Computers are instructed to function through instruction. A logical set of instructions to a computer, to perform a task, is called a program. The language in which these instructions are written will vary from computer to computer.
However these languages can be classified into four categories:
First generation: Machine language
In this computers were programmed into binary notations of “0” and “1”. This was residing on CPU. This was tedious to write and was prone to errors.
Second-generation: Assembly language
Because of limitations of 1st generation language, assembly language was developed in which each operation was represented by Mnemnic code. This was further improved by consideration of symbolic assembly codes. This helped programmer to represent-to-represent memory location, variables and instructions with names. This kind of programming is fast but requires high knowledge of CPU and machine’s instruction set. Speed was the primary consideration during this language but it lacked portability.
Example: Auto code; SAP, SPS
Third generation: High Level Languages.
To avoid dependency on knowledge of hardware, new languages were developed. This provided the programmers to concentrate more on problem solving. Also it was machine independent and provided, comparative ease of use and learning, improving portability, debugging facilitates, lower cost of software.
Fourth generation: Very High Level Language
Third generation languages were not user friendly. To provide more user friendliness, usability by non-programmers and more independence of operating system, fourth generation language were developed.
Also third generation language was more procedure dependent on how something is done. Most fourth generation languages are nonprocedural.
Example: APL, CPS, Power Builder, Access
Fifth generation:
Third generation languages were not user friendly. To provide more user friendliness, improvements in fourth generation were carried out, like no programming knowledge, little or no coding, computer added design and graphics. This also provided users facilities to extract information from databases and represent in their own form, till now for which they were dependent on programmers.
Example: PROLOG
FUTURE
Powerful languages of future will combine procedure code and nonprocedure statements together with flexibility of interactive screen applications, a powerful way of developing application program. Languages telling, what is accomplished but not on how?
SYSTEM DEVELOPMENT LIFE CYCLE
A SYSTEM is defined as inter related group of procedures to perform an activity or achieve an objective. In designing a system there are nine steps, which together is called SDLC or “SOFTWARE DEVELOPMENT LIFE CYCLE”. The steps are
1 Requirement Study
2 Requirement Specification
3 Feasibility Analysis
4 Final Specification
5 Hardware Study
6 System Design
7 System Implementation
8 System Evaluation
9 System Modification
1. Requirement Study
Objective of information is to meet organization needs to take proper decisions. At top-level decision is taken to use computer for getting information. The next step involves discussion with user to find out what exactly is expected from system. Discussion also evolves priority among different applications.
2. Requirement Specification
In this stage, existing manual operations are to be studied and discussed with users to find out what activity is to be computerized to provide computer-generated information. The activities to be computerized are listed and priority is set.
3 Feasibility Analysis
After deciding on activities to be computerized, it is to be decided whether it is feasible to implement it. During this stage all constraints are to be considered under which the system is to be implemented and operated. Requirements of hardware, software, manpower is to be estimated and cost is to be calculated. Comparision between cost and benefits (direct & indirect) is carried out to justify computerization. Report consisting of all this information is called “Feasibility Report”.
4. Final Specification
After management studies the feasibility report and approves the report, specifications are to be drawn. This involves drawing of a flow chart, indicating the different activities in the system and the inter relationship between the activities; what controls will be built in, how many programs will be written. Success of the computerization will, to a large extent, will depend on how good the specifications have been drawn.
There is a possibility that this specification may under go some changes as the computerization of the system progresses. These changes are to be documented to substantiate the correctness of the system.
5. Hardware Study
Based on the final specifications, the configuration of hardware and support software is decided. It is to be decided whether existing hardware/software will meet this additional load. If not then the same has to be procured and installed before the software is ready.
6. System Design.
This involves logical design of the system. Also involves logical design of each program. This involves, what inputs will be considered, what processing will be carried out on these input, what outputs will be generated after processing, what controls will be generated which will indicate the correctness of the program. During this phase File/Database structure is prepared and keys are indicated for accessing it. Also considered is the test data to test the program and system test. Finally the implementation plan is drawn.
7. System Implementation.
During this phase, all programs are written & tested, database is created, test data is created, and system/operational and user documentation is prepared.
8. System Evaluation
After the system is operating for a certain period, it is evaluated to find out whether it is meeting all the objectives for which it was designed. If not, modifications required are noted down and plan to carry out these changes, is drawn.
9. System Modification
Conditions under which a business organization functions, are always changing. This may arise because of new business opportunities, Changes in government regulations, change in business competition. A good computer system flexible to accommodate changes, at the same time should not lose control in operation.
NETWORKING:
It is sharing of information and resources between more than one computers connected. It provides communication tools to share information and resources.
Networking developed due to changes taking place in information processing models like:
Centralized Processing
Distributed Processing
CENTRALIZED PROCESSING:
Initially organizations used computers to process information at high speed. This required that the computers should be large. These large computers called “MAINFRAME” used to store and organize data. Users entered data on this Mainframe using “Local” device called Terminal, through communication hardware, so that a single Mainframe computer could service requests from multiple users. Mainframe used to provide all data storage and computing facilities while Terminals used to be only an Input/Output device.
When organizations wanted Mainframes to share information and services with other Mainframes in the organization, thought of Networking started.
DISTRIBUTED PROCESSING:
As computer industry started maturing, small Personal Computers were created which allowed individuals total control over their computer. These PC power resulted in new way of computing called Distributed Processing.
Instead of centralizing all storage and processing with a single Mainframe, it was distributed to a group of PC by creating subsets of processing. This generated the need of Networking.
TYPES OF NETWORK:
Networks can be broadly classified into two broad categories:
* PEAR TO PEAR
In this type of network, there are no dedicated servers that mean there is no hierarchy.
All computers are equal and are known as pears. Each computer functions as both client and a server and no one are assigned to be an administrator for network. Each user decides what data to be shared on network.
Normally this type is ideal for small workgroups, may be less than 10 computers.
This is very cost effective in terms of hardware and operating system as each machine can function on different level of performance.
This does not require central administrative control, as each is independent.
This does not require security arrangement.
Example:
Microsoft Windows NT workstation.
Microsoft Windows for workgroup
Microsoft Windows 95/98
* SERVER BASED
In this type of network a server is used as dedicated server and is not used as client or workstation. However as the size of network increases there can be more than one server.
In today’s environment networks are server based.
Server takes care of
Centralized data
Service requests from clients / workstations
Security of files.
Security of directories.
As said there can be multiple servers, depending on requirement of organization, connected together in a LAN OR WAN, like
File and Print server:
Managing access and use it and edit before putting it back to file and print server.
Application server:
This differs from File and Print server in a way that database remains on server but only the information requested by client is downloaded into client computer’s memory.
Mail server:
This manages electronic messaging between users
Fax server:
This manages fax traffic into and out of network.
Directory services Server
This handles access rights of users to locate, store and secure information on network.
Today computer Networks are classified by size, distance covered and structure.
Local Area Network:
It is a combination of hardware and transmission media that is relatively small, not exceeding ten Km and uses one type of transmission media. It is normally restricted to a building.
Metropolitan Area Network:
It is larger than LAN and covers area of a city. It used different hardware and transmission media.
Wide Area Network:
WAN has no boundaries of distance, hardware and transmission media
WAN can be also called “Enterprise Area Network” if it is only to be used by one organization.
All Networks require three elements:
1 At least two computers who can share information and/or resources
2 A method or Pathway for contracting each other
3 Rules which are to be observed to communicate
As such networking is:
1 Something to share---------------called Network Services
2 Pathway to contact---------------called Transmission Media
3 Rules for Communication-------called Protocols
NETWORK SERVICES:
It is the capabilities that Networked Computers share. It is provided by combination of different Hardware and Software. Network Services provide following services:
File Sharing Services
Print Services
Messaging Services
Application Services
Database Services
File Services:
Rapidly move files from place to place
Use storage efficiently
Manage multiple copies of same file
Backup critical data
Print Services:
Provide multiple access
Eliminate distance constraint
Handle simultaneous requests
Share specialized equipments
Messaging Services:
Pass computer generated notes and files between users
Integrate Electronic Mail and Voice Mail Systems
Operate Object Oriented Software with Objects distributed through out Network
Route and Share data using Workflow documents
Organize and manage users and device information directories
Application Services
Database Services
DATA COMMUNICATION TRANSMISSION LAYERS
Physical Layer:
Coordinates rules for transmitting bits and defines:
Physical Network Structure
Mechanical and Electrical specifications
Bit transmission encoding and timing
Data Link Layer: (Normally used in single network)
Organizes physical layer bits (0,1) into logical groups called FRAMES
Detect errors
Control data flow
Identify computers in Network
Network Layer: (Normally used in multiple network)
Move data to specific Network
Switching( how one makes connections)
Routing ( from one to another network)
Gateway (from one to another country)
Transport Layer:
Identify Service requestor
Identify Service provider
Manage Segment development
Identify connection services
Care address resolution
Session Layer:
Communication between service provider and service requester
Establish, maintain, synchronize and manage dialog
Presentation Layer:
Transforms data into mutually agreed format which can be understood
by each network application and computer in the network.
Here data can be encrypted or decrypted or compressed or expanded.
Application Layer:
Provides Protocols necessary to perform Network Service functions.
Like: File, Print, Message, and Application, Database
LEADING PROTOCOLS:
IPX/SPX: Sequence Packet Exchange
Internet Packet Exchange
TCP/IP: Transmission Control Protocol
Internet Protocol
X.25 Used by IBM
NETWORK TRANSMISSION MEDIA:
Computers use Electric Voltage OR Electromagnetic Waves to send signals.
The physical path thru which these waves travel is called Transmission Media. The ability of transmission media to accommodate different ranges of waves, decides the type of transmission media.
For Example:
Kilo Hertz Power and Telephone
Mega Hertz Radio Waves
Giga Hertz Micro Waves (Dish Antenna)
Tera Hertz Infrared (TV)
Photon Energy Ultra Violet
X rays
Gamma rays
Transmission media is classified as cable OR wireless.
Transmission media usage depends on:
Cost
Ease of installation
Capacity
Attenuation - weaken during transmission
Immunity - Effect of Electromagnetic waves
BANDWIDTH:
Range of cycle frequencies measured in Hertz OR cycles per second. But normally indicated in bits per second transmitted.
CABLE Types:
Twisted Pair Cable
Unshielded
Shielded
Coaxial
Fiber Optic
Twisted Pair:
Twisted pair uses copper wire because it is good conductor of electrons. But when two copper wires conduct signals in close proximity, certain amount of electro magnetic waves occurs which is called CROSS TALK. But because of electro magnetic range used, Twisted Pair also transmits and receives unwanted signals from other media. In twisted pair each cable generates electro magnetic waves, which is cancelled by electro magnetic waves generated by other.
UTP is a set of twisted pair with simple plastic encasement. It varies from 1 to 5 depending on quality. Commonly used is category 3 used in general. Category 5 has more twists per foot and higher insulation.
UTP is connected thru a device RJ45 (4pair) or RJ11 (2pair). These are connected to both end of cable called Patch Cord.
STP is shielded in foil shielding. Apple and IBM environment mostly use it.
Coaxial:
It is composed of two conductors that share a common axis. Center is relatively solid copper encased in plastic foam. A wire mesh surrounds this foam. Over this a thick and tough insulating tube is covered.
Different types of Coaxial cable are used in different cases depending on standards and Ohms (a measurement unit of resistance to direct/ indirect currents)
50 ohms RG8 - used in Ethernet
75 ohms RG59 - Used in cable TV
Fiber Optic:
It is made of light conducting glass surrounded by glass (called cladding) and a tougher outer sheet.
The center core provides light path.
Fiber cable can be Single Mode OR Multi mode.
Types of Fiber Optic cable are considered on the basis of composition and core/cladding size.
Common types are:
8.3 Micron core - 125-micron cladding Single mode
62.5 Micron core - 125-micron cladding Multi mode
50 Micron core - 125-micron cladding Multi mode
100 Micron core - 140-micron cladding Multi mode
Wireless:
Following are the wireless media:
Radio Wave Short wave
Very High Frequency (VHF) FM radio and TV
Ultra high frequency (UHF) Radio and TV
Micro Wave Earth based (VSAT)
Satellite based
Infrared Remote Control
Cable Media Connectors:
T Connector
BNC Connector (British Naval Connector)
Terminator
RJ45/ RJ11 ( Jack)
NIC card (Network Interface Card)
Transmission Media Devices:
REPEATER/ AMPLIFIER
Amplifier amplifies all incoming Electro Magnetic waves including undesirable noise. Other type of Amplifier, called Repeater, strips data from Noise, reconstructs signals and then retransmits.
HUB
It is a device to connect multiple PC in a network.
Connection is through ports available in Hub.
There are three types of Hub:
Active Hub: This amplify signals
They connect all PC and ensure that each receives signal
It has own power supply
Passive Hub: They do not amplify signals
They do not have power supply
They connect all PC and ensure each receives signal
Now not used
Intelligent: In addition to all facilities of Active Hub:
Hub They offer Management and Maintenance of System
They can also be used to identify problems on Network
SWITCH:
It is a device which connects multiple PC
It is more intelligent than HUB
It is capable of inspecting data packets for source, destination and
forwarding accordingly
Conserves Bandwidth, as it sends information to only intended PC.
It is a replacement to Intelligent Hub and have all facilities offered by
Intelligent Hub
It is cheaper
MODEM:
It modulates and Demodulates signals.
Converts digital signals to analog to pass through PSTN OR
Microwave trans receivers.
Converts Analog / Microwave signals from PSTN OR Microwave trans receivers and coverts to digital signals to be accepted by computers.
Modem is necessary because PSTN and Microwave media use Electro Magnetic Waves BUT Computers use Electric Pulse
It is also used when signals are not powerful enough. It can be used to amplify signals
ROUTER:
Routers are used to connect two Networks (LAN)
Can have multiple Ports dedicated to separate Networks.
Supports multiple Protocols
Traffic Mngt: Manages traffic of Network, using intelligent path selection based on traffic load and speed of transmission media.
Share Information: It shares Routing information with other Routers in Network as they identify which connections are busy
Filtering Bad Data: Does not forward information, which has no correct Network address.
Performance: Performs complex tasks.
NETWORK TOPOLOGY:
Bus Topology:
It is a Network connection in which all Nodes(PC) are connected directly to a main OR Backbone Cable (BUS)
Bus needs to be terminated at both ends of Cable so that signals are reflected back
Signals travel in both directions
Advantages:
It is very easy to install
Requires least amount of cable
It is cheap
Not dependent on any device
Disadvantages
Signal quality deteriorates with increase in number of PC
It is difficult to trouble shoot because it can be any where
Media failure affects network
(Draw a Diagram as explained in Class)
Ring Topology
PCs are connected in a ring OR circle.
Signals generated from one PC is passed on from PC to PC in a single direction
Signal is regenerated at each device
Advantages
Uses least amount of cable
Simple to install
It is cheap
Not dependent on any device
Disadvantages
Signal quality deteriorates with increase in number of PC
It is difficult to trouble shoot because it can be any where
Media failure affects network
(Draw a Diagram as explained in Class)
Star Topology
It is a network where PCs are connected to a central device, like Hub or Switch via a point-to-point connection using a transmission media
PC send information on the network, central device receives signals and sends signals to all PCs on Network.
Advantages:
It is commonly used and has been successfully in Telephone System
It is easy to configure and reconfigure
It is easy to manage as all data is sent to central device
It is easy to locate problem
Problems are automatically detected in media OR NIC OR Workstation
Disadvantages:
All devices are affected by media OR device failure
(Draw a Diagram as explained in Class)
DATA BASE and RELATIONAL DATA BASE:
Database Management System is software, which allows users to:
Define data
Create data
Maintain data
Controlled access to data
DBMS includes common utilities such as
Report Writer
Application Development & Design Tools
Database Administration
Example: Oracle, Access, DB, Sybase, and Informix
In DBMS actual data is separated from programs.
Entity: A thing of significance about which information need to be known (This is similar to record)
Attribute: Characteristics, which describe or qualify an entity, are attribute (This is similar to fields in a record)
Domain: Set of possible value that an attribute can take is domain.
In DBMS users are classified as:
Database Administrator
End Users
Application Programmers
An integral part of any system is set of procedures that control the behavior of the system.
Database can be single user OR multi user
In multi user, data is shared and integrated (same information is not duplicated)
Database can be single tier, 2 tier, 3 tier
In 2 tier, different software is required at server level and client level
(Client/Server)
In 3 tier, a middle ware is required which provides a way for client of
one database to access data of another database.
WHY DBMS:
Data is valued asset of an organization, which is to be maintained for use by users. The advantages are mainly:
Proper maintenance of data
Proper access to users
Proper security of data
Data Models:
It is a way of explaining the logical layout of data and relationship of various parts to each other and as a whole.
Types of Database:
Hierarchical:
Based on tree structure with one root and several sub trees.
Each item having just one link
Access begins with root and travels to desired location
Network:
It contains many links among various items of data
Allows access from multiple directions
Relational:
All data are kept in table form with relations
Much more flexible and easy to use
Retrieval time is reduced
Allows the use of distributed database which was not available in
Hierarchical and network
Maintains directory of tables, column names and data type
Along with users and privileges
Database Schema:
Describes the data and the relationship. It is used to describe the conceptual organization of database, which is defined during design process. Designing is carried out using a language called DDL (Data Definition Language), which is provided by software vendor. It is used to create Tables and fields within each table.
Actual population of database is accomplished using DML (Data Manipulation Language). Most commonly used language is SQL (structured query language)
Modules of DBMS:
Data: Stored Data Manager
Run time Database Processor
Software: DDL compiler
System and Data Directory
Query compiler
Users: DDL DBA
Privileged commands DBA
Interactive query User
Pre compilers Programmers
Host language compilers Programmers
DATA
Data is the information collected from actual operation about entity collection of information about similar entities is a file.
DATABASE MANAGEMENT
Database is a highly ordered collection of files.
It can be defined in multiple ways and contexts. However in universally it can be defined, as “Management, creation and maintenance of data in a useful and productive order”
With reference to computers, creation and maintenance of data files are carried out in different ways.
1. SEQUENTIAL FILE
Records are physically stores in ascending or descending order of primary key. Record can be retrieved only in sequential order. This can be on tape or disk.
2. HASH FILES.
Records are not stored in ascending or descending order of primary key. Each record is assigned to disk storage, a disk address by obtaining from applying a standard calculating logic to the primary key (hashing routine).
When a record is to be retrieved hashing routine is applied to primary key and the disk address is obtained to retrieve the record.
3. INDEX SEQUENTIAL FILES
Records are stored in ascending order of primary key. When the records are written down, an access method using primary key, creates an index to provide disk address.
Since records are stored in ascending order, it can be retrieved sequentially also.
ADVANTAGES OF DATABASE MANAGEMENT SYSTEM over
FILE MANAGEMENT SYSTEM
1 The context and organization of database can be changed without effecting application software.
2 Change of hardware/software does not have effect on application software
3 Sharing of data by multiple application programs each program feeling as if data is organized for it’s requirement
4 There is central control of data, ensuring security and integrity of data.
5 System identifies common data and avoids duplication. However for better performance of system some duplication is allowed.
6 Relationship between data items should be specified.
7 System preserves consistency of data value and relationship by using various data editing methods.
8 Access to data is controlled through access rights. Access can be for individual item or group of items.
9 System maintains performance base to provide timely information.
10 Control over data for deletion, changes and additions to satisfy legal, accounting and auditing requirements.
MODELS IN DATABASE MANGEMENT SYSTEM
1. Hierarchical Database
This type of database represents data as tree structure composed of a hierarchy of data records.
To retrieve the data in hierarchical system one has to know the final path to the record, which results in multiple requests to data manager and for this one has to remember, how the data is represented in storage.
2. Network
When database becomes complex, hierarchical structure is not suitable to take care of complexity. As such hierarchical model is modified by allowing records to have multiple parent child relationship. These relations are known as sets in Network database model.
To retrieve the data in network system one has to know the final path to the record, which result in multiple requests to data manager and for this one has to remember, how the data is represented in storage.
3. Relational
In relational model, the database can be represented as a simple collection of two-dimensional table, which in other words is called relational database management system.
In relational model only one type of data structure exists-- table.
In relational model, the relationships between tables are created on a temporary basis by an end user request. For retrieve the data, relational system provides an automatic navigator for the data you want and you do not have to remember, how the data is represented in storage.
Let us take a case of a warehouse.
A record in WAREHOUSE describes a warehouse with Warehouse number as the primary key (say WHNUMB). Other fields can be
Description of part
CITY
FLOOR
A record for PART describes type of part with Part Number as primary key (say PTNUM). Other fields can be
Description of part
Bin number
A record for INVENTORY gives the quantity (say QTY) of a type of part (identified by PTNUMB) in a warehouse (identified by WHNUMB)
Consider the relationship among three.
There is a relationship between WAREHOUSE and INVENTORY
There is relationship between PART and INVENTORY
EXPLANATION
For any warehouse there must be an inventory record for each type of part in the warehouse. Thus for each WAREHOUSE record, there must be many INVENTORY records, while for each INVENTORY record there can be only one WAREHOUSE record.
EXAMPLE
WAREHOUSE TABLE PART TABLE
WHNUMB CITY FLOOR PTNUMB DESCRIPTION BIN
WH1 MUMBAI 5 P2 TRANSISTOR 2C1
WH2 DELHI 3 P4 INDUCTOR 3F2
WH3 CALCUTTA 2 P7 TRANSISTOR 2C1
P9 CAPACITOR 4B2
INVENTORY TABLE
WHNUMB PTNUMB QTY BIN
WH1 P4 675 3F2
WH1 P7 250 2C1
WH1 P9 340 4B2
WH2 P2 280 2C1
WH2 P4 200 3F2
WH2 P9 270 4B2
WH3 P2 550 2C1
WH3 P4 330 3F2
PARENT CHILD RELATIONSHIP
Since for one record in WAREHOUSE there are many records in INVENTORY, we can say that the WAREHOUSE record is the “PARENT” record and INVENTORY records are “CHILD” wise.
INVENTORY TABLE PARENT WISE (WHNUMB)
WHNUMB PTNUMB QTY BIN
WH1 P4 675 3F2
WH1 P7 250 2C1
WH1 P9 340 4B2
WH2 P2 280 2C1
WH2 P4 200 3F2
WH2 P9 270 4B2
WH3 P2 550 2C1
WH3 P4 330 3F2
INVENTORY TABLE CHILD WISE (PTNUMB)
WHNUMB PTNUMB QTY BIN
WH2 P2 280 2CI
WH3 P2 550 2C1
WH1 P4 675 3F2
WH2 P4 200 3F2
WH3 P4 330 3F2
WH1 P7 250 2C1
WH1 P9 340 4B2
WH2 P9 270 4B2
Introduction to Computer Terminology
Centralised Data processing system
Types of hardware configuration, peripherals etc.
Systems Software:
DOS, NOVELL, UNIX
Operating system functions
Translators
Compilers
Interpreters
Application Software
Programming Languages and their characteristics
Foxpro
C
Introduction to
Electronic Spread Sheet
Data Base Management Systems
Word Processors
Graphic User Interfaces
Introduction to Foxpro
Writing simple programs
Introduction to Relational Data Base
CONTENTS
Evaluation of Computers
Numbering System
Computer and Devices
Operating System/ Interpreter/ Compiler
Languages
System Development Life Cycle
Networking
Network Design
Network Communication Media
Network Connecting Devices
Models of File Management System
Models of Database Management System
Advantages of DBMS over File Management System
Management Information System
Internet
WEB
EVALUATION OF COMPUTERS
First generation computers (1957 - 58)
They were large, not reliable and use of vacuum tubes
1) Tremendous heat caused more failures.
2) Punched cards were used to feed data and instructions.
3) Instructions were coded in binary system, which was cumbersome. And time consuming.
4) Assembler was used to translate Assembly language program in binary language required
5) Chore space proer and heat generation high second generation Computer ( 1959 – 1964)
Second Generation Computers (1959-64)
Vacuum tubes were replaced with Transistors. This resulted in
1) Less heat generation, lesser space and power required.
2) More reliable and faster processing.
3) Higher Storage capacity.
4) Punch card used.
5) Magnetic tape were used as Storage media
6) Programming techniques were refined resulting in new high level languages like Fortran Cobol
Third generation Computer (1965 – 1971)
Transistors were replaced by Integrated Circuits (IC) Which consisted of hundreds of electronic components, put on a Silicon Chip.
1) Smaller Size of Computer
2) Cheaper Computers
3) Lesser power required
4) Faster Processing
5) More reliability
IBM first introduced with system 360 series. This technology change introduced concept of mini Computers and remote terminal. Remote Terminals allowed processing from distant locations by connecting terminals to center computer and using its capabilities. This concept was known as time-sharing and many users were able to run separate programs simultaneously.
Forth generation Computers (1972 – till sate)
IC were further integrated calling it large scale Integration
(LSI) which is also called Microchip, which further helped in development of Microprocessor.
With Lesser Cost of Computer its usage increased at home, education and business.
Fifth generation Computers (Future)
This is in development stage to build intelligent computer, which will be able to converse with humans in natural language. Computer will be able to take decisions on learned experience (Attificial Intelligence) and memory capabilities
Computer will be able to learn, make inferences, and make decisions.
NUMBERING SYSTEM
We have seen that computer can understand two characters namely “0” and “1”.
Each of this is called BIT, abbreviation for Binary Digit.
A set of letters A to Z, a to z, punctuation, 32 control character, 129 special character, totaling 256 character is called Alphanumeric Character Set.
Consider a number 4568
Each digit is determined by
The digit itself
The position of the digit in number
The base of the number itself
Base is the number of distinct symbols used in that system.
Example: In decimal system there are ten symbols as 0,1,2,3,4,5,6,7,8,9, so it’s base is 10.
In Binary system there are two symbols namely 0 and 1 so the base is 2.
Since 2 bits is not sufficient for representing these 256 character set, a set of 8 digits is considered and this combination of 8 digits is called BYTE.
2 raised to power 8 = 2x2x2x2x2x2x2x2 = 256
Like us, computer expresses information in WORDS. A combination of bits is called a WORD. The length of a Word will vary from computer to computer. Word length determines the information OR number of bits CPU moves internally or externally.
For convenience data whether in memory or hard disk, is measured in bytes or higher denominations of byte
1024 bytes = Kilobyte (Kb)
10,48,576 bytes = Megabyte (Mb)
107,37,41,824 bytes = Gigabyte (Gb)
* We are familiar with a system where we have number 0 to 9. This is called Decimal system.
We have also seen the computer can understand only 0 and 1.
* Representation of character by 0 and 1 is called Binary System.
• Initially, combinations of 6 bits were considered for representation of a character. This is called Binary Coded Decimal System.
To increase the representation of number of characters the length was increased from 6 to 8. However this time two thoughts prevailed for representation, namely ASCII and EBCDIC.
* ASCII – American National Standard Code.
For Information Interchange.
This system uses 7 bits for a byte. 2 raise to 7 = 128 character representation.
* EBCDIC – Extended Binary Coded Decimal Interchange Code.
This system uses 8 bits for a byte, 2 raise to 8 = 256 character representation.
Take an example:
Decimal number Binary number
0 00
1 01
2 10
3 11
4 100
5 101
6 110
7 111
8 1000
9 1001
In above we see that
We require 2 bits to represent decimal numbers 0 to 3
We require 3 bits to represent decimal numbers 4 to 7
We require 4 bits to represent decimal numbers 8 and 9
That means each decimal number representation in binary requires on average 3.2 bits.
In ASCII we have seen we use 7 bits. The eight bit is used for error checking what is called parity check. Computers have either odd or even bit parity checks. After conversion from decimal to binary if total 1 is even and computer is odd bit parity check then 1 is added at right most level to make it odd parity check.
We have seen that a decimal digit takes 3.2 bits in binary form. Thus 10 digits of decimal will take about 32 bits of binary form. It will be difficult to write such long strings of 1 and 0 and chances of error will be more. So IBM devised EBCDIC system where 16 is used a base viz. 0,1,2,3,4,5,6,7,8,9,A, B, C, D, E, and F.
CONVERSION FROM DECIMAL TO BINARY
Consider a decimal number 25. This will be expressed in decimal form as (25) base 10. If this is to be converted in binary with base 2, the conversion will be as under:
1 Divide the number by base that is 2
2 Write down the remainder
Repeat step 1 & 2 till quotient is zero
2 |25 1
2 |12 0
2 |6 0
2 |3 1
2 |1 1
(1x2) + (1x2) + (0x2) + (0x2) + 1x2)
QUESTIONS
1 Convert decimal 36 in binary
2 Convert decimal 2345 in binary
CONVERSION FROM DECIMAL TO HEXADECIMAL
Consider a decimal number 25. This will be expressed in decimal form as (25) base 10. if this is to be converted in hexadecimal with base 16, the conversion will be as under:
1. Divide the number by base that is 16
2. Write down the remainder
Repeat step 1 & 2 till quotient is zero
16 |25 9
16 |1 1
|0
(1x16) + (9x16)
16+9 = 25
QUESTIONS
1 convert decimal 36 in binary
2 convert decimal 2345 in binary.
CONVERSION FROM DECIMAL FRACTIONS TO BINARY
The decimal fraction is expressed as sum of negative power of 2.
STEPS
1 Multiply a decimal fraction by 2
2 The integer part will be most significant bit of the binary fraction
3 The fractional part of the answer is multiplied by 2 to obtain the next significant bit of the binary fraction.
4 The procedure is continued till the fractional part is zero.
EXAMPLE
1 Find binary equivalent of 0.7
0.70 x 2 = 1.40 1 most significant bit
0.40 x 2 = 0.80 0
0.80 x 2 = 1.60 1
0.60 x 2 = 1.20 1
0.20 x 2 = 0.40 0
----------------------------
0.40 x 2 = 0.80 0 recurs beyond this point
Thus (0.7) base 10 = (0.B3) (3) base 16
2 Find binary equivalent of 0.5625
0.5625 x 2 = 1.125 1 most significant bit
0.125 x 2 = 0.250 0
0.250 x 2 = 0.500 0
0.500 x 2 = 1.000 1
(0.5625) base 10 = (0.1001) base 2
CONVERSION OF DECIMAL FRACTION IN HEXADECIMAL FRACTIONS
1 Multiply a decimal fraction by base 16
2 The integer part will be most significant bit of the binary fraction
3 The fractional part of the answer is multiplied by 16 to obtain the next the next significant bit of the binary fraction
4 The procedure is continued till the fractional part is zero
EXAMPLE
1 Find binary equivalent of 0.7
0.70 x 16 = 11.20 11 most significant bit
0.20 x 16 = 03.20 3
---------------------------------------------
0.20 x 16 = 3.20 3 recurs beyond this point
Thus (0.7) base 10 = (0.B3) (3) base 16
2 Find binary equivalent of 0.5625
0.5625 x 16 = 9.0000 9 most significant bit
(0.5625) base 10 = (0.9) base 16
COMPUTER AND DEVICES
Having in general talked about computer, let us see technically how a computer can be described.
A computer can be thought as a machine that would carry out instructions obediently, uncritically with high speed and without emotions.
As human being, we use emotions which is called commonsense but computers does not have judgement and commonsense.
Example: A colonel sent his order to post office with order
“ Go to post office and buy ten number of 25 paisa stamp”
Orderly went to post office and did not return for a long period. Colonel went in search of him to post office and found orderly standing there with stamps in his hand. When colonel asked him, pet came the reply that he was ordered to buy ten 25-paisa stamps but not ordered to return with them.
Computer does not understand commonsense and will stop functioning in such cases, which is called hanging of the system.
ALGORITHM: is a finite sequence of instructions to solve a problem and has following basics:
Acceptance of input
Processing rules, which are unambiguous and can be carried out
Each instruction must be sufficiently basic
Time to carry out instructions must be finite.
Must produce output.
It has been derived from “al-khowarizmi” an Arabic mathematician “Abu Jafar Mohammed ibn Musa al-khowarizmi”. Father of Jafar, son of Musa and resident of al-khowarizmi.
We have seen that the computer system consists of three segments
Input
Hardware devices from which information is received
Central processing
Hardware, which does processing of information
Output
Hardware devices, which help in producing results of processing by central processing.
INPUT DEVICES
Punch card
This is a thin card of 18.8 cm x 8.3 cm size. It is divided into 80 columns and 12 rows. Rows are numbered A, B and 0 to 9 starting from top to down. Combination of holes in rows of each column occupies a character.
Keyboard
There are alfa keys, Numeric keys, special character keys, and some functional keys.
INPUT/OUTPUT DEVICES
Floppy
It is a flexible magnetic coated plastic of 5 ¼” diameter.
When power is turned on, a small motor rotates the floppy drive under a magnetic head.
It is of sizes 8”, 5 ¼”, 3 ½” and capacity 128 KB, 256 KB, 768 KB, 1.44 MB
Floppy can be Hard sector/ Soft sector floppies.
In hard sector floppy, sides to be used, location & number of tracks, are set by hardware characteristics of floppy and the floppy drive. This cannot be changed.
In soft sector floppy, location, size and number of sectors within a track are defined by software. A sector may have 128/256/512/1024 characters. This is done when the floppy is being formatted.
HARD DISK
It can be conceived of having many floppies put together. Disk operations are controlled by “Disk Controller”. Hard disk can have multiple platters each having two sides. The portion occupied by the same track in all platters, together is called a cylinder.
Number of read/write heads will depend on number of platters in a disk.
Formatting a floppy or disk, divides the sectors into four sections.
BOOT RECORD :
It contains a shore program to start the process of loading of operating system. . Other Information on this will vary on type of format being used.
File Allocation Table:
FAT follows boot record and contains information on how disk has been formatted and also the Map of location of sectors used by data files.
It keeps information of each file, its name, size and start sector.
DATA SPACE
Remaining sectors occupies the data. Data is kept in the form of cluster which in a floppy. Number of sectors in a cluster will vary from type of diskette being used. In one-sided floppy, it is one sector and in double sided floppy, it is a pair of adjacent sectors.
FIXED / REMOVABLE DISK
Now a days all disks are fixed. Previously on mainframe there used to be disks, which can be removed and inserted. In today’s context, we have concept “ Hot swappable disk” which means that when computer is working disks can be removed and new disks can be inserted.
COMPACT DISK
OUTPUT DEVICES
MONITOR
Called VDU, where information is displayed, either through keyboard or from CPU.
PRINTERS
Printers are of types, namely serial and line printers Inkjet and Laser.
Dot matrix
Line dot matrix
Daisy Wheel
Drum
Chain
Inkjet
Laser
Serial printers take one character at a time with printer head moving across the line. Characters are sent from memory to printer, decoded by printer electronics and printed by activating pins.
Line printers print aline at a time. These are also called parallel printers.
Each printer has a logic card for conversion of signals in to characters and also a memory, which is called a buffer memory.
Inkjet Printers
Laser Printers
CENTRAL PROCESSING UNIT
Processor
This is the main, which controls the operations of compute system. This microprocessor delegates certain control functions to other chips and CPU in free to attend to its own work. These are called device controllers and housed on different slots of motherboard. To name a few, for example:
Interrupt Controller
Direct Memory Access Controller (DMA)
Clock Generator
CRT Controller
Disk controller
Diskette controller
Arithmetic Logic Unit
All these controllers along with CPU are fixed on a board and connected through a circuitry, which is called the motherboard.
The main circuitry to which different circuits are connected is called a bus. There are mainly two types of bus, namely Address and Data.
Address bus transmits the addresses of memory cells and devices.
Data bus in conjunction with address bus carry data throughout computer
MEMORY
Memory is made up of large number of cells, each cell capable of storing one bit. Cells may be organized as set of addressable words. In such a situation if time to store and retrieve a word is independent of the address of the word than it is called Random Access Memory. This is main memory of the computer. Presently these are made of semiconductor.
If the memory cell information is permanently written than it is called Read Only Memory.
Different type of RAM is
SRAM; Static Random Access Memory
DRAM; Dynamic Random Access Memory
Virtual / Secondary Memory is the device on which additional information is written. Information is brought to and from this device. It can be hard disk, Tape, CD, and Floppy.
Cache memory is a part of memory controlled by cache controller, which stores the contents of frequently accessed memory locations and their addresses.
OPERATING SYSTEM
Software can be classified as Systems software and Application software.
An operating System, which can be classified as part of systems software, is a series of programs used by the computer to manage its operations as well as allow the users to interact with the computer through various devices.
It is a set of programs that acts as middle layer between application software and computer hardware. Computers with different hardware architecture will have different operating systems.
When the computer is turned on, it is the first program, which is loaded in computer memory and will remain in memory till the computer is turned off.
Operating Systems are developed in two ways:
OS developed with software in mind and Networking features are added later on. This is susceptible to bugs. Example: Microsoft Windows.
OS developed with Networking in mind and software features are added later on. These are robust OS. Example: UNIX, NETWARE
Major functions of Operating systems are
Memory Management
Space/Disk management
Input / Output devices management.
TYPES of Operating System
Single User
This means that one person can work at a time and only one job can be executed at a particular time.
Best example is of PC working under DOS (Disk Operating System) and the user working on a “Spread Sheet” or “MS-Office.”
Example: Dos, WINDOWS 95/98
Multitasking Operating System
This type of operating system allows a user to process more than on job at a time. Monitor screen can be split into a number of sections (windows) each one running a separate job. One window may be running a spreadsheet while other may be on MS- office.
Example: UNIX
Multi-user Operating System.
This allows a number of users to share a single computer connected to each user PC. Each user is able to share the same operating system and files of the main computer.
Example: WINDOWS NT, Novell Netware
INTERPRETER
Interpreter is a software program, which reads one line of a program, changes it into machine code and then executes it. This procedure is followed with each line of that program till that program is executed fully.
If this program is to be run again, the interpreter has to go through the same procedure again.
This method is slow and takes more storage space. However it has the advantage that it can be interrupted during execution, changed if there are mistakes and then restarted. Because of this reason this is used for testing/debugging of programs.
COMPLIERS
This software program to create machine code from a source program. This process is called compilation. Programs written in Languages cannot run unless they are compiled first.
The program generated after compilation called executable, in run on computer to process the job. This is faster operation as interpretation stage is eliminated.
LANGUAGES
Computers are instructed to function through instruction. A logical set of instructions to a computer, to perform a task, is called a program. The language in which these instructions are written will vary from computer to computer.
However these languages can be classified into four categories:
First generation: Machine language
In this computers were programmed into binary notations of “0” and “1”. This was residing on CPU. This was tedious to write and was prone to errors.
Second-generation: Assembly language
Because of limitations of 1st generation language, assembly language was developed in which each operation was represented by Mnemnic code. This was further improved by consideration of symbolic assembly codes. This helped programmer to represent-to-represent memory location, variables and instructions with names. This kind of programming is fast but requires high knowledge of CPU and machine’s instruction set. Speed was the primary consideration during this language but it lacked portability.
Example: Auto code; SAP, SPS
Third generation: High Level Languages.
To avoid dependency on knowledge of hardware, new languages were developed. This provided the programmers to concentrate more on problem solving. Also it was machine independent and provided, comparative ease of use and learning, improving portability, debugging facilitates, lower cost of software.
Fourth generation: Very High Level Language
Third generation languages were not user friendly. To provide more user friendliness, usability by non-programmers and more independence of operating system, fourth generation language were developed.
Also third generation language was more procedure dependent on how something is done. Most fourth generation languages are nonprocedural.
Example: APL, CPS, Power Builder, Access
Fifth generation:
Third generation languages were not user friendly. To provide more user friendliness, improvements in fourth generation were carried out, like no programming knowledge, little or no coding, computer added design and graphics. This also provided users facilities to extract information from databases and represent in their own form, till now for which they were dependent on programmers.
Example: PROLOG
FUTURE
Powerful languages of future will combine procedure code and nonprocedure statements together with flexibility of interactive screen applications, a powerful way of developing application program. Languages telling, what is accomplished but not on how?
SYSTEM DEVELOPMENT LIFE CYCLE
A SYSTEM is defined as inter related group of procedures to perform an activity or achieve an objective. In designing a system there are nine steps, which together is called SDLC or “SOFTWARE DEVELOPMENT LIFE CYCLE”. The steps are
1 Requirement Study
2 Requirement Specification
3 Feasibility Analysis
4 Final Specification
5 Hardware Study
6 System Design
7 System Implementation
8 System Evaluation
9 System Modification
1. Requirement Study
Objective of information is to meet organization needs to take proper decisions. At top-level decision is taken to use computer for getting information. The next step involves discussion with user to find out what exactly is expected from system. Discussion also evolves priority among different applications.
2. Requirement Specification
In this stage, existing manual operations are to be studied and discussed with users to find out what activity is to be computerized to provide computer-generated information. The activities to be computerized are listed and priority is set.
3 Feasibility Analysis
After deciding on activities to be computerized, it is to be decided whether it is feasible to implement it. During this stage all constraints are to be considered under which the system is to be implemented and operated. Requirements of hardware, software, manpower is to be estimated and cost is to be calculated. Comparision between cost and benefits (direct & indirect) is carried out to justify computerization. Report consisting of all this information is called “Feasibility Report”.
4. Final Specification
After management studies the feasibility report and approves the report, specifications are to be drawn. This involves drawing of a flow chart, indicating the different activities in the system and the inter relationship between the activities; what controls will be built in, how many programs will be written. Success of the computerization will, to a large extent, will depend on how good the specifications have been drawn.
There is a possibility that this specification may under go some changes as the computerization of the system progresses. These changes are to be documented to substantiate the correctness of the system.
5. Hardware Study
Based on the final specifications, the configuration of hardware and support software is decided. It is to be decided whether existing hardware/software will meet this additional load. If not then the same has to be procured and installed before the software is ready.
6. System Design.
This involves logical design of the system. Also involves logical design of each program. This involves, what inputs will be considered, what processing will be carried out on these input, what outputs will be generated after processing, what controls will be generated which will indicate the correctness of the program. During this phase File/Database structure is prepared and keys are indicated for accessing it. Also considered is the test data to test the program and system test. Finally the implementation plan is drawn.
7. System Implementation.
During this phase, all programs are written & tested, database is created, test data is created, and system/operational and user documentation is prepared.
8. System Evaluation
After the system is operating for a certain period, it is evaluated to find out whether it is meeting all the objectives for which it was designed. If not, modifications required are noted down and plan to carry out these changes, is drawn.
9. System Modification
Conditions under which a business organization functions, are always changing. This may arise because of new business opportunities, Changes in government regulations, change in business competition. A good computer system flexible to accommodate changes, at the same time should not lose control in operation.
NETWORKING:
It is sharing of information and resources between more than one computers connected. It provides communication tools to share information and resources.
Networking developed due to changes taking place in information processing models like:
Centralized Processing
Distributed Processing
CENTRALIZED PROCESSING:
Initially organizations used computers to process information at high speed. This required that the computers should be large. These large computers called “MAINFRAME” used to store and organize data. Users entered data on this Mainframe using “Local” device called Terminal, through communication hardware, so that a single Mainframe computer could service requests from multiple users. Mainframe used to provide all data storage and computing facilities while Terminals used to be only an Input/Output device.
When organizations wanted Mainframes to share information and services with other Mainframes in the organization, thought of Networking started.
DISTRIBUTED PROCESSING:
As computer industry started maturing, small Personal Computers were created which allowed individuals total control over their computer. These PC power resulted in new way of computing called Distributed Processing.
Instead of centralizing all storage and processing with a single Mainframe, it was distributed to a group of PC by creating subsets of processing. This generated the need of Networking.
TYPES OF NETWORK:
Networks can be broadly classified into two broad categories:
* PEAR TO PEAR
In this type of network, there are no dedicated servers that mean there is no hierarchy.
All computers are equal and are known as pears. Each computer functions as both client and a server and no one are assigned to be an administrator for network. Each user decides what data to be shared on network.
Normally this type is ideal for small workgroups, may be less than 10 computers.
This is very cost effective in terms of hardware and operating system as each machine can function on different level of performance.
This does not require central administrative control, as each is independent.
This does not require security arrangement.
Example:
Microsoft Windows NT workstation.
Microsoft Windows for workgroup
Microsoft Windows 95/98
* SERVER BASED
In this type of network a server is used as dedicated server and is not used as client or workstation. However as the size of network increases there can be more than one server.
In today’s environment networks are server based.
Server takes care of
Centralized data
Service requests from clients / workstations
Security of files.
Security of directories.
As said there can be multiple servers, depending on requirement of organization, connected together in a LAN OR WAN, like
File and Print server:
Managing access and use it and edit before putting it back to file and print server.
Application server:
This differs from File and Print server in a way that database remains on server but only the information requested by client is downloaded into client computer’s memory.
Mail server:
This manages electronic messaging between users
Fax server:
This manages fax traffic into and out of network.
Directory services Server
This handles access rights of users to locate, store and secure information on network.
Today computer Networks are classified by size, distance covered and structure.
Local Area Network:
It is a combination of hardware and transmission media that is relatively small, not exceeding ten Km and uses one type of transmission media. It is normally restricted to a building.
Metropolitan Area Network:
It is larger than LAN and covers area of a city. It used different hardware and transmission media.
Wide Area Network:
WAN has no boundaries of distance, hardware and transmission media
WAN can be also called “Enterprise Area Network” if it is only to be used by one organization.
All Networks require three elements:
1 At least two computers who can share information and/or resources
2 A method or Pathway for contracting each other
3 Rules which are to be observed to communicate
As such networking is:
1 Something to share---------------called Network Services
2 Pathway to contact---------------called Transmission Media
3 Rules for Communication-------called Protocols
NETWORK SERVICES:
It is the capabilities that Networked Computers share. It is provided by combination of different Hardware and Software. Network Services provide following services:
File Sharing Services
Print Services
Messaging Services
Application Services
Database Services
File Services:
Rapidly move files from place to place
Use storage efficiently
Manage multiple copies of same file
Backup critical data
Print Services:
Provide multiple access
Eliminate distance constraint
Handle simultaneous requests
Share specialized equipments
Messaging Services:
Pass computer generated notes and files between users
Integrate Electronic Mail and Voice Mail Systems
Operate Object Oriented Software with Objects distributed through out Network
Route and Share data using Workflow documents
Organize and manage users and device information directories
Application Services
Database Services
DATA COMMUNICATION TRANSMISSION LAYERS
Physical Layer:
Coordinates rules for transmitting bits and defines:
Physical Network Structure
Mechanical and Electrical specifications
Bit transmission encoding and timing
Data Link Layer: (Normally used in single network)
Organizes physical layer bits (0,1) into logical groups called FRAMES
Detect errors
Control data flow
Identify computers in Network
Network Layer: (Normally used in multiple network)
Move data to specific Network
Switching( how one makes connections)
Routing ( from one to another network)
Gateway (from one to another country)
Transport Layer:
Identify Service requestor
Identify Service provider
Manage Segment development
Identify connection services
Care address resolution
Session Layer:
Communication between service provider and service requester
Establish, maintain, synchronize and manage dialog
Presentation Layer:
Transforms data into mutually agreed format which can be understood
by each network application and computer in the network.
Here data can be encrypted or decrypted or compressed or expanded.
Application Layer:
Provides Protocols necessary to perform Network Service functions.
Like: File, Print, Message, and Application, Database
LEADING PROTOCOLS:
IPX/SPX: Sequence Packet Exchange
Internet Packet Exchange
TCP/IP: Transmission Control Protocol
Internet Protocol
X.25 Used by IBM
NETWORK TRANSMISSION MEDIA:
Computers use Electric Voltage OR Electromagnetic Waves to send signals.
The physical path thru which these waves travel is called Transmission Media. The ability of transmission media to accommodate different ranges of waves, decides the type of transmission media.
For Example:
Kilo Hertz Power and Telephone
Mega Hertz Radio Waves
Giga Hertz Micro Waves (Dish Antenna)
Tera Hertz Infrared (TV)
Photon Energy Ultra Violet
X rays
Gamma rays
Transmission media is classified as cable OR wireless.
Transmission media usage depends on:
Cost
Ease of installation
Capacity
Attenuation - weaken during transmission
Immunity - Effect of Electromagnetic waves
BANDWIDTH:
Range of cycle frequencies measured in Hertz OR cycles per second. But normally indicated in bits per second transmitted.
CABLE Types:
Twisted Pair Cable
Unshielded
Shielded
Coaxial
Fiber Optic
Twisted Pair:
Twisted pair uses copper wire because it is good conductor of electrons. But when two copper wires conduct signals in close proximity, certain amount of electro magnetic waves occurs which is called CROSS TALK. But because of electro magnetic range used, Twisted Pair also transmits and receives unwanted signals from other media. In twisted pair each cable generates electro magnetic waves, which is cancelled by electro magnetic waves generated by other.
UTP is a set of twisted pair with simple plastic encasement. It varies from 1 to 5 depending on quality. Commonly used is category 3 used in general. Category 5 has more twists per foot and higher insulation.
UTP is connected thru a device RJ45 (4pair) or RJ11 (2pair). These are connected to both end of cable called Patch Cord.
STP is shielded in foil shielding. Apple and IBM environment mostly use it.
Coaxial:
It is composed of two conductors that share a common axis. Center is relatively solid copper encased in plastic foam. A wire mesh surrounds this foam. Over this a thick and tough insulating tube is covered.
Different types of Coaxial cable are used in different cases depending on standards and Ohms (a measurement unit of resistance to direct/ indirect currents)
50 ohms RG8 - used in Ethernet
75 ohms RG59 - Used in cable TV
Fiber Optic:
It is made of light conducting glass surrounded by glass (called cladding) and a tougher outer sheet.
The center core provides light path.
Fiber cable can be Single Mode OR Multi mode.
Types of Fiber Optic cable are considered on the basis of composition and core/cladding size.
Common types are:
8.3 Micron core - 125-micron cladding Single mode
62.5 Micron core - 125-micron cladding Multi mode
50 Micron core - 125-micron cladding Multi mode
100 Micron core - 140-micron cladding Multi mode
Wireless:
Following are the wireless media:
Radio Wave Short wave
Very High Frequency (VHF) FM radio and TV
Ultra high frequency (UHF) Radio and TV
Micro Wave Earth based (VSAT)
Satellite based
Infrared Remote Control
Cable Media Connectors:
T Connector
BNC Connector (British Naval Connector)
Terminator
RJ45/ RJ11 ( Jack)
NIC card (Network Interface Card)
Transmission Media Devices:
REPEATER/ AMPLIFIER
Amplifier amplifies all incoming Electro Magnetic waves including undesirable noise. Other type of Amplifier, called Repeater, strips data from Noise, reconstructs signals and then retransmits.
HUB
It is a device to connect multiple PC in a network.
Connection is through ports available in Hub.
There are three types of Hub:
Active Hub: This amplify signals
They connect all PC and ensure that each receives signal
It has own power supply
Passive Hub: They do not amplify signals
They do not have power supply
They connect all PC and ensure each receives signal
Now not used
Intelligent: In addition to all facilities of Active Hub:
Hub They offer Management and Maintenance of System
They can also be used to identify problems on Network
SWITCH:
It is a device which connects multiple PC
It is more intelligent than HUB
It is capable of inspecting data packets for source, destination and
forwarding accordingly
Conserves Bandwidth, as it sends information to only intended PC.
It is a replacement to Intelligent Hub and have all facilities offered by
Intelligent Hub
It is cheaper
MODEM:
It modulates and Demodulates signals.
Converts digital signals to analog to pass through PSTN OR
Microwave trans receivers.
Converts Analog / Microwave signals from PSTN OR Microwave trans receivers and coverts to digital signals to be accepted by computers.
Modem is necessary because PSTN and Microwave media use Electro Magnetic Waves BUT Computers use Electric Pulse
It is also used when signals are not powerful enough. It can be used to amplify signals
ROUTER:
Routers are used to connect two Networks (LAN)
Can have multiple Ports dedicated to separate Networks.
Supports multiple Protocols
Traffic Mngt: Manages traffic of Network, using intelligent path selection based on traffic load and speed of transmission media.
Share Information: It shares Routing information with other Routers in Network as they identify which connections are busy
Filtering Bad Data: Does not forward information, which has no correct Network address.
Performance: Performs complex tasks.
NETWORK TOPOLOGY:
Bus Topology:
It is a Network connection in which all Nodes(PC) are connected directly to a main OR Backbone Cable (BUS)
Bus needs to be terminated at both ends of Cable so that signals are reflected back
Signals travel in both directions
Advantages:
It is very easy to install
Requires least amount of cable
It is cheap
Not dependent on any device
Disadvantages
Signal quality deteriorates with increase in number of PC
It is difficult to trouble shoot because it can be any where
Media failure affects network
(Draw a Diagram as explained in Class)
Ring Topology
PCs are connected in a ring OR circle.
Signals generated from one PC is passed on from PC to PC in a single direction
Signal is regenerated at each device
Advantages
Uses least amount of cable
Simple to install
It is cheap
Not dependent on any device
Disadvantages
Signal quality deteriorates with increase in number of PC
It is difficult to trouble shoot because it can be any where
Media failure affects network
(Draw a Diagram as explained in Class)
Star Topology
It is a network where PCs are connected to a central device, like Hub or Switch via a point-to-point connection using a transmission media
PC send information on the network, central device receives signals and sends signals to all PCs on Network.
Advantages:
It is commonly used and has been successfully in Telephone System
It is easy to configure and reconfigure
It is easy to manage as all data is sent to central device
It is easy to locate problem
Problems are automatically detected in media OR NIC OR Workstation
Disadvantages:
All devices are affected by media OR device failure
(Draw a Diagram as explained in Class)
DATA BASE and RELATIONAL DATA BASE:
Database Management System is software, which allows users to:
Define data
Create data
Maintain data
Controlled access to data
DBMS includes common utilities such as
Report Writer
Application Development & Design Tools
Database Administration
Example: Oracle, Access, DB, Sybase, and Informix
In DBMS actual data is separated from programs.
Entity: A thing of significance about which information need to be known (This is similar to record)
Attribute: Characteristics, which describe or qualify an entity, are attribute (This is similar to fields in a record)
Domain: Set of possible value that an attribute can take is domain.
In DBMS users are classified as:
Database Administrator
End Users
Application Programmers
An integral part of any system is set of procedures that control the behavior of the system.
Database can be single user OR multi user
In multi user, data is shared and integrated (same information is not duplicated)
Database can be single tier, 2 tier, 3 tier
In 2 tier, different software is required at server level and client level
(Client/Server)
In 3 tier, a middle ware is required which provides a way for client of
one database to access data of another database.
WHY DBMS:
Data is valued asset of an organization, which is to be maintained for use by users. The advantages are mainly:
Proper maintenance of data
Proper access to users
Proper security of data
Data Models:
It is a way of explaining the logical layout of data and relationship of various parts to each other and as a whole.
Types of Database:
Hierarchical:
Based on tree structure with one root and several sub trees.
Each item having just one link
Access begins with root and travels to desired location
Network:
It contains many links among various items of data
Allows access from multiple directions
Relational:
All data are kept in table form with relations
Much more flexible and easy to use
Retrieval time is reduced
Allows the use of distributed database which was not available in
Hierarchical and network
Maintains directory of tables, column names and data type
Along with users and privileges
Database Schema:
Describes the data and the relationship. It is used to describe the conceptual organization of database, which is defined during design process. Designing is carried out using a language called DDL (Data Definition Language), which is provided by software vendor. It is used to create Tables and fields within each table.
Actual population of database is accomplished using DML (Data Manipulation Language). Most commonly used language is SQL (structured query language)
Modules of DBMS:
Data: Stored Data Manager
Run time Database Processor
Software: DDL compiler
System and Data Directory
Query compiler
Users: DDL DBA
Privileged commands DBA
Interactive query User
Pre compilers Programmers
Host language compilers Programmers
DATA
Data is the information collected from actual operation about entity collection of information about similar entities is a file.
DATABASE MANAGEMENT
Database is a highly ordered collection of files.
It can be defined in multiple ways and contexts. However in universally it can be defined, as “Management, creation and maintenance of data in a useful and productive order”
With reference to computers, creation and maintenance of data files are carried out in different ways.
1. SEQUENTIAL FILE
Records are physically stores in ascending or descending order of primary key. Record can be retrieved only in sequential order. This can be on tape or disk.
2. HASH FILES.
Records are not stored in ascending or descending order of primary key. Each record is assigned to disk storage, a disk address by obtaining from applying a standard calculating logic to the primary key (hashing routine).
When a record is to be retrieved hashing routine is applied to primary key and the disk address is obtained to retrieve the record.
3. INDEX SEQUENTIAL FILES
Records are stored in ascending order of primary key. When the records are written down, an access method using primary key, creates an index to provide disk address.
Since records are stored in ascending order, it can be retrieved sequentially also.
ADVANTAGES OF DATABASE MANAGEMENT SYSTEM over
FILE MANAGEMENT SYSTEM
1 The context and organization of database can be changed without effecting application software.
2 Change of hardware/software does not have effect on application software
3 Sharing of data by multiple application programs each program feeling as if data is organized for it’s requirement
4 There is central control of data, ensuring security and integrity of data.
5 System identifies common data and avoids duplication. However for better performance of system some duplication is allowed.
6 Relationship between data items should be specified.
7 System preserves consistency of data value and relationship by using various data editing methods.
8 Access to data is controlled through access rights. Access can be for individual item or group of items.
9 System maintains performance base to provide timely information.
10 Control over data for deletion, changes and additions to satisfy legal, accounting and auditing requirements.
MODELS IN DATABASE MANGEMENT SYSTEM
1. Hierarchical Database
This type of database represents data as tree structure composed of a hierarchy of data records.
To retrieve the data in hierarchical system one has to know the final path to the record, which results in multiple requests to data manager and for this one has to remember, how the data is represented in storage.
2. Network
When database becomes complex, hierarchical structure is not suitable to take care of complexity. As such hierarchical model is modified by allowing records to have multiple parent child relationship. These relations are known as sets in Network database model.
To retrieve the data in network system one has to know the final path to the record, which result in multiple requests to data manager and for this one has to remember, how the data is represented in storage.
3. Relational
In relational model, the database can be represented as a simple collection of two-dimensional table, which in other words is called relational database management system.
In relational model only one type of data structure exists-- table.
In relational model, the relationships between tables are created on a temporary basis by an end user request. For retrieve the data, relational system provides an automatic navigator for the data you want and you do not have to remember, how the data is represented in storage.
Let us take a case of a warehouse.
A record in WAREHOUSE describes a warehouse with Warehouse number as the primary key (say WHNUMB). Other fields can be
Description of part
CITY
FLOOR
A record for PART describes type of part with Part Number as primary key (say PTNUM). Other fields can be
Description of part
Bin number
A record for INVENTORY gives the quantity (say QTY) of a type of part (identified by PTNUMB) in a warehouse (identified by WHNUMB)
Consider the relationship among three.
There is a relationship between WAREHOUSE and INVENTORY
There is relationship between PART and INVENTORY
EXPLANATION
For any warehouse there must be an inventory record for each type of part in the warehouse. Thus for each WAREHOUSE record, there must be many INVENTORY records, while for each INVENTORY record there can be only one WAREHOUSE record.
EXAMPLE
WAREHOUSE TABLE PART TABLE
WHNUMB CITY FLOOR PTNUMB DESCRIPTION BIN
WH1 MUMBAI 5 P2 TRANSISTOR 2C1
WH2 DELHI 3 P4 INDUCTOR 3F2
WH3 CALCUTTA 2 P7 TRANSISTOR 2C1
P9 CAPACITOR 4B2
INVENTORY TABLE
WHNUMB PTNUMB QTY BIN
WH1 P4 675 3F2
WH1 P7 250 2C1
WH1 P9 340 4B2
WH2 P2 280 2C1
WH2 P4 200 3F2
WH2 P9 270 4B2
WH3 P2 550 2C1
WH3 P4 330 3F2
PARENT CHILD RELATIONSHIP
Since for one record in WAREHOUSE there are many records in INVENTORY, we can say that the WAREHOUSE record is the “PARENT” record and INVENTORY records are “CHILD” wise.
INVENTORY TABLE PARENT WISE (WHNUMB)
WHNUMB PTNUMB QTY BIN
WH1 P4 675 3F2
WH1 P7 250 2C1
WH1 P9 340 4B2
WH2 P2 280 2C1
WH2 P4 200 3F2
WH2 P9 270 4B2
WH3 P2 550 2C1
WH3 P4 330 3F2
INVENTORY TABLE CHILD WISE (PTNUMB)
WHNUMB PTNUMB QTY BIN
WH2 P2 280 2CI
WH3 P2 550 2C1
WH1 P4 675 3F2
WH2 P4 200 3F2
WH3 P4 330 3F2
WH1 P7 250 2C1
WH1 P9 340 4B2
WH2 P9 270 4B2