Basics Of Computers in Short..

What is Computer?
Computer can be defined as an Electronic Device with ability to:

1. Accept data supplied by the user.

2. Input, store & execute instructions.

3.Perform mathematical & logical operations.

4. Output results according to user requirements.

Anatomy of a Computer System:

A system is a set of components that work together to accomplish one or more common goals.  A computer system can be viewed as a system of three major Components: --

Computer Hardware:

Includes mechanical, electrical & electronic parts.

Computer software:

Are the programs, instructing the computer how to process the data & generate Required Information.

Note: The failure of any system component leads to the failure of the system as a whole.

Functional Components of a Computer:

Hardware of any computer system can be broadly classified into:           
Central Processing Unit and Peripherals:

The heart of the computer is called the CPU or processor it performs: -

A:         Arithmetic Operations (add, subtract, multiply, & divide)

B:         Logical Operations (logical comparisons like true or false)

C:         Input Output Operations (accepting data to process & generate output)

D:         Internal Data Movements.

E:         Data Manipulation.

To perform those operations CPU has components like:

Arithmetic Logic Unit:

Which performs Actual Calculations & comparisons.

Control Unit:

Co-Ordinates operations of the hardware, flow of data, its execution & the instruction that are fed into the memory via CPU.  CU fetches the instructions & data from memory unit, decodes them & sends them to ALU.  Output from ALU is fetched by CU & sent it to the various parts of  the Computer.

Memory Unit (MU):

It is the main store of whole data, instructions, intermediate & final results from main store into ALU.  All instructions or data are stored in MU before being used by ALU & CU.  The main store is divided into a number of storage locations which can be accessed by a unique number of address.

Classification of computer as for Purpose

Analog Computers:

Measures physical quantities & convert them to numeric Values.  These computers are used for scientific & engineering purposes.

Digital Computers:

They count the numbers, letters, or other special symbols.  These computers are used in different applications.

Hybrid Computers:

Features of Analog & Digital computers are combined to create a Hybrid Computing System.

According To Size Computers Are Classified As:

1)         Micro Computer:

Is a smallest of Computer inside of which ALU & CU are combined on a single chip called a Microprocessor.  Micro Computers are used as Home Computers.  It has two types of memory: -

A: Random Access Memory (RAM)

Where programs & data are held during processing temporarily.  Data stored in RAM is lost whenever machine is switched off.

B: Read Only Memory (ROM)

Where permanent instruction of data are held.  ROM does not require continuous supply of power to retain its contents.

2)         Mini Computer:

Are more powerful than micro computers & can support several users.  Having larger RAM & backing storage capacity & can process data more quickly.  These computers are used by medium size organization to process payrolls & financial accounts.

3)         Mainframes:

Are very large computers with a very high capacity of main store.  As they can process larger amounts of data very quickly, they are used by big companies, banks etc. as their main computers.

4)         Super computers:

Complex scientific applications like whether forecasting require a large amount of data to be manipulated within a short time.  Large Super Computers with faster processing using multiple processors & superior technology are used complex tasks requiring a lot of computational power.

Computers Ability:

1. Faster in Processing.

2. Performs repetitive task without error.

3. Accurate in Calculations.

4. Work at constant efficiency i.e. computers speed remains same over a number of years.

5. Versatile: They can do variety of jobs depending on their instructions fed to them & their hardware characteristics.

Computer’s Limitations

1. It completely depends on human being.

2. Computers can not think of their own.

3. Computers can not detect or flows in logic or data.

4. Tasks to the computers have to be described in detail.

Input devices:

Input devices are required to get raw data into the computer, they are: -

Keyboard:

Resembles the typewriter.  Computer keyboard has three categories of keys.

Alphanumeric keys:

Comprises of [A-Z or a-z], Numbers [0-9], & Other Characters like space, . / ‘ “; : + - ( ) { } [] # @ $ % ^ * ! ? Etc.

Special Keys:

Perform specific tasks as enter, backspace, space, ctrl, ins, shift, caps lock, alt, etc.

Function:

Used to perform a set of operations by single keystrokes.

Mouse:

Enables the user to manipulate a pointer or arrow on a terminal or micro Computer screen.  The cursor moves in direction of mouse movement.

Out Put Devices

Visual Display Unit (VDU):

Used for interactive processing i.e. data that is being keyed in, is displayed on the screen.  Messages & processed information are also displayed on the screed.  Combination of keyboard & VDU is referred to as Visual Display Terminal (VDT) which is an Input Output Device.

Printers:

Most common form of computer output is printed output, also called as hard copy output.

Data Storage Devices

Main Memory:

Memory unit of CPU is place where programs or instructions & data are stored while processing.  Device consists of a number of storage locations.  Each storage location may be identified by a unique number, which is called its address.  During processing data may be stored in any location, which is identified by the address of the location.  Storage area may be designed to store fixed number of characters, which are treated as single entity or word.  Each character in a computer is represented in storage location by a string of binary number 0’s & 1’s that are treated as a unit.  This unit or set of binary digits is called as a byte &, a byte consists of grouping of 8 bits.

RAM:

In primary storage section of Random Access Memory it is possible to read from & write on to any location within it by specifying its location.  New data can be written onto any location.  While doing so the previous existing data is erased.  RAM chips are or two types: - 1] Static & 2] Dynamic.

ROM:

Read Only Memory chips ROM contains data that can be read randomly when required, but can not be written onto them.  Data is hardwired on to this chips at the manufacturing time & the user can not change them.  Even in power loss we can retain data.

PROM:

Programmable Read Only Memory.  Critical & lengthy operations can be converted in to micro programs & fused into a Programmable Read Only Memory chips.  A fused can not be restored.  PROM can be programmed at once.

EPROM:

Electrically Programmable Read Only Memory makes it possible for user to repeatedly erase & reprogram the ROM.

EEPROM:

Electrically Erasable Programmable Read Only Memory can be programmed through use of special electrical pulses.  It is possible to integrate the circuitry into computer.  So that EEPROM does have to remove from its socket for programming.

NUMBER SYSTEMS:

All digital computers store numbers, letters, & other characters in coded form.  Code used to represent characters is binary code, made up of binary digits or bits.  Every character is represented by strings or 0,s & 1’s.  The only digits found in the binary numbering system.  A sequence of 8 bits is called as byte.  1024 bytes makes a Kilobyte.  1024 kilobytes makes a Gigabyte.
8 bits                     =          1 Byte 
1024 Bytes           =          1 Kilobyt
1024 Kilobytes    =          1 Megabytes
1024 Megabytes  =          1 Gigabyte.

Smallest unit of data is the data field.  Collection of related data items treated as single unit is called a record.  Records are grouped to form files.

A file is number of related records that are treated as a unit representing a particular transaction.   


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