Computer Basic Knowledge

C

omputer:                                                                                                                                             

                   The word computer comes from the word “compute”, which means to calculate. Hence, a computer is normally considered to be a calculating device, which can perform, arithmetic operations at enormous speed.

Data processing:

                    The activity of processing data using a computer is called data processing. Data processing consists of three sub-activities: capturing the input data, manipulating the data and managing the output results.

Characteristics of computers:

(1)    Automatic, (2) Speed, (3) Accuracy, (4) Diligence, (5) versatility, (6) Power of remembering, (7) No I. Q, (8) No feelings.

***Charles Babbage, a nineteenth century Professor at Cambridge University, is considered the father of modern digital computers.

*** The Electronic Numerical Integrator & Calculating (ENIAC) was the first all electronic computer (The ENIAC 1943-46).

*** The Electronic Discrete Variable Automatic Computer (EDVAC 1946-52).

***The Electronic Delay Storage Automatic Calculator (EDSAC 1947-49).

*** The Universal Automatic Computer (UNIVAC1951) was the first digital computer.

***Transistor was invented at Bell Laboratories in1947 by John Bardeen, William Shockley and Walter Brattain.

***High-level programming language (FORTRAN, COBOL, ALGOL & SNOBOL)

*** In 1958 Jack St Clair Kilby and Robert Noyce invented the first integrated circuit (ICs).

ð  Small scale integration (SSI).

ð  Medium scale integration (MSI).

ð  Large scale integration (LSI).

ð  Very large scale integration (VLSI).

The five basic operations performed by computer system are:

ð  Inputting

ð  Storing

ð  Processing

ð  Outputting

ð  Controlling

Input device:

                         An input device is an electromechanical device which accepts data from the outside world and translates them. The input devices are

ð  Keyboard

ð  Mouse

ð  Scanner

ð  Microphone

ð  Webcam

ð  Vision based

Output device:

                             An output device is an electromechanical device which accepts data from a computer and translates them into a from which is suitable for use by the outside world.

ð  Monitors

ð  Printers

ð  Plotters(World map)

ð  Screen image projector

ð  Voice response system

ð  Speaker

Input unit:

                   The input unit allows data and instruction to be fed to the computer system from the outside world.

Output unit:

                   The output unit allows the computer system to supply the information, obtained from the data processing, to the outside world.

Storage unit:

                   The storage unit of a computer system holds the data and instructions to be processed and the intermediate and final results of processing.

The two types of Storage unit:

ð  Primary storage unit (Main memory) is a volatile.

ð  Secondary storage unit (is a non-volatile).

Control unit:

                      The control unit of a computer system manages and coordinates the operation of all the other components of the computer system

Central processing unit (CPU):

                        The control unit and the arithmetic logic unit of a computer system are jointly known as the CPU. The CPU is the brain of computer system.

*** The Binary Coded Decimal (BCD) is a 6-bit code, which can represent 64 different characters.

***The extended Binary-Coded Decimal Interchange Code (EBCDIC) is an 8-bit code, which can represent 256 different characters.

***American Standard Code for Information Interchange (ASCII) is one of the most popular computer codes. It is two types

ð  ASCII-7

                                  ASCII-7 is a 7 code, which can represent 128 different characters. The first 3 bits are used as zone bits, and the last 4 bits indicate the digit.

ð  ASCII-8

                                ASCII-8 is an 8 code, which can represent 256 different characters.

Registers:

                  In order to handle this process satisfactorily and to speed up the rate of information transfer the computer uses a number of special memory units. The functions of these registers are described below.

ð  Memory Address Register (MAR).

ð  Memory Buffer Register (MBR).

ð  Program Control Register (PC).

ð  Accumulator Register (A).

ð  Instruction Register (I).

ð  Input / Output Register (I/O).

Processor:

Types of Processor

ð  CISC Processor (Complex Instruction Set Computer).

ð  RISC Processor (Reduced Instruction Set Computer).

ð  EPIC Processor (Explicitly Parallel Instruction Computer).

*** A Computer’s main memory is built of a volatile RAM chips.

Random Access Memory (RAM): 

                        It is a non volatile memory chip, in which data are stored permanently & cannot be altered by the programmer

***Programmable Read –Only Memory (PROM).

***Erasable Programmable Read-Only Memory (EPROM) chips can be reprogrammed to store new information. EPROM chips are of two types

ð  Ultra Violet EPROM (UVEPROM)

ð  Electrically EPROM (EEPROM) is also known as flash memory.

Cache memory:

                           Cache memory is an extremely fast, small memory between CPU and main memory, whose access time is closer to the processing speed of the CPU. Its acts as a high-speed buffer between CPU and main memory.

Magnetic tape:

             Magnetic tape is the most popular sequential-access storage device. It consists of a plastic ribbon, usually ½ inch or ¼ inch wide, which is coated with a magnetizable recording material.

Magnetic disk:

              Magnetic disk is the most popular direct-access storage device. It consists of a thin, circular plate made of material or plastic, which is coated on both sides with a magnetizable recording material. It is broadly two types

ð  Floppy disks

                          Floppy disk is a round, flat piece of flexible plastic coated with magnetic oxide. (They are were introduced by IBM in 1972). A floppy disk can be very easily loaded into or unloaded from a floppy disk drive (Floppy disk drive is a device, which is used to read/write data from/to floppy disks). In case of currently used floppy-disk drives, the rotational speed of a floppy disk is of the order of 300 to 400rpm, & the data transfer rate is of the order of 10 to 30 kilobytes/second.

ð  Hard disks

                Hard disks are the primary on line secondary storage device for most computer system today. Hard disks are made of rigid metal (frequently Aluminum).It is three types…..

                        1)  Zip/Bernoulli disks.

                        2)  Disk Packs.

                        3)  Winchester Disks.

Optical Disk;

                Optical Disk can store extremely large amount of data in a limited space. Laser beam technology is used for recording/reading of data on the disk, for this reason Optical disks are known as Laser Disks  or Optical Laser Disks. All Optical Disks are round platters. The two most p[opular types of Optical Disks in use today are ……….

ð  CD-ROM

                  CD-ROM stands for Compact Disk-Read-Only Memory. It is a spin-off of music CD technology, and works much like the music CDs in music systems. The CD-ROM disk is a shiny, silver color metal disk of 5 ¼ inch (12cm) diameter. It has a storage capacity about 650 Megabytes.

ð  WORM Disk

                 WORM stands for Write-Once Read Memory. WORM disks allow the users to create their own CD-ROM disks by using a CD-recordable (CD-R) drive.

***Redundant Array of Inexpensive Disks (RAID).

Printers:

                 Printers are the most commonly used output devices today for producing hard-copy output. The various printers in used today are ….

ð  Dot-Matrix Printers:

                              Dot-Matrix Printers are character printers, which print one character at a time. Dot-Matrix Printers are normally slow with speeds usually ranging between 30 to 600 characters per second.

ð  Inkjet Printers:

                              Inkjet Printers are character printers, which from characters and all kinds of images by spraying small drop of ink on to the paper. Inkjet Printers are slower than Dot-Matrix Printers with speeds usually ranging between 40 to 300 characters per second.

ð  Drum Printers:

                              Drum Printer is expensive. A drum printer with 132 characters per line and supporting a character set of 96 characters will have altogether 12672 characters embossed on its surface.

ð  Chain/ Brand Printers.

                                                        

ð  Laser Printers:

                                 Laser Printers are page printer, which print one page at a time. Laser printer is faster in printing speed than other printers. Low speed laser printers can print 4 to 12 pages per minute. Very high speed laser printers are available now & can print 500 to 1000 pages pr minute.

Plotters:

             Plotters are ideal output device for architects, engineers, city planners 7 others who need to routinely generate high precision, hard-copy, graphic output of widely varying sizes. There are two types of Plotters….

ð  Drum Plotter.

ð  Flatbed Plotter.

Software:

               Actually software made by many programs. The term software refers to the set of computer programs, procedures and associated documents which describes the programs and how they are to be used. Software means a collection of programs whose objective is to enhance the capabilities of the hardware.  There are two major software are………..

ð  System Software:

                            

                         System Software is a set of one or more programs, designed to control the operation and extend the processing, capability of a computer system. Some of the most commonly known types of system software are………

1)      Operating Systems.

2)      Programming Language translation.

3)      Communication Software.

4)      Utility Programs.

ð  Application Software:

                                Application Software is a set of one or more programs, designed to solve a specific problem, or do a specific task. Some of the most commonly known types of Application Software are………               

1)      Word-Processing Software.

2)      Spreadsheet Software.

3)      Database Software.

4)      Graphics Software.

5)      Personal Assistance Software.

6)      Education Software.

7)      Entertainment Software.

Pseudo code:

                   Pseudocode is another programming analysis tools, which is used for planning program logic.”Psedo” means imitation or false and “code” refers to the instruction written in a programming language.

*** Program Design Language (PDL)

Programming Language/ Computer Language:

                    A language that is acceptable to a computer system is called a Computer language or programming language. The process of writing instructions in such a language for an already planned program is called programming or coding.

All computer language can be broadly classified into the following three categories….

ð  Machine Language.

                   Although computers can be programmed to understand many different computer languages, there is only one language understood by the computer without using a translation program.

ð  Assembly Language.

                       A language, which allows instructions and storage locations to be represented by letters and symbols, instead of numbers, is called an assembly language or Symbolic Language.

Compiler:

                   A compiler is a translator program, which translates a high level language program into its equivalent machine-language program.

Interpreter:

                   An Interpreter is translator program, which translates high-level languages program into its equivalent machine-language program.

High level Languages:

                There are some high Level Language are….

ð  FORTRAN

                 FORTRAN stands for FORmula TRANslation. It is one of the first and oldest High level Languages.

ð  COBOL

                 COBOL stands for Common Business Oriented Language. It is the most widely used programming language for business-oriented applications.

ð  BASIC

       BASIC stands for Beginners All-purpose Symbolic Instruction Code. BASIC is available in almost all personal computers and even in some pocket calculators.

Operating System:

                    An Operating System is an integrated set of programs that controls the resources of a computer system and provides its users with an interface or virtual machine that is more convenient to use than the bare machine.

Virtual memory:

                     Virtual memory is a memory management scheme that allows the execution of processes, which might not be completely loaded in the main memory. The three basic concepts used for the realization of Virtual memory are on-line secondary storage (memory) swapping and demand paging.