COMPONENTS OF THE COMPUTER

HARDWARE:Hardware is the physical or circuitry part of the computer, and includes input devices, output devices, storage devices, power supply unit, CPU and the auxiliary circuit elements. When we instruct a computer to do some task, we enter the instruction and data though the Input Device into it. The computer stores these sets of instructions and data in its Memory, and at the time of execution, it executes the instructions given to its “Central Processing Unit (CPU)”, the result of which appears on the Output Devices like monitor, printer etc.

A. Input devices: - Input devices are those units through which we send instruction and data to the machine or computers. We use several types of input units as: Keyboard, Optical Character Reader (OCR), Magnetic Ink Character Reader/Recognizer (MICR), Mark Sense Reader, Graphics Tablet, Touch Screen, Light Pen, Mouse and now a day through Speech.

B. Central Processing Unit (CPU): - the CPU receives data and instruction, stores them temporarily and then processes the data as per the instructions. The part contain the following three units:

(a) Memory Unit (MU),(b) Arithmetic and Logic Unit (ALU), and (c) Control Unit (CU).

(a) Memory Unit: - The memory unit holds (stores) all data, instruction and result. The memory consists of hundreds of thousand of cells called storage location. Each Capable of storing one word of information in the form of 0’s and 1’s (which is binary number system) in order to access any previously stored data from the memory, we have to supply the address of the cell in which it has been stored. Thus address is the memory location in where the data is stored .the content of that address is the stored data. Actually at the time of programming, the computer maintain the address of each variable and data in its own system and in most of the cases we do not need to know the actual address of each data stored. The computer itself maintains this automatically. The storage system of a computer can be classified in two major groups. They are:(i) Primary Memory or Main Memory or Volatile Memory or Semi-conductors Memory or Internal Memory.(ii) Secondary Memory or Auxiliary Memory or Non-volatile Memory or Magnetic-core Memory or External Memory.

(i) Primary memory : -

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At the time of typing a program, we can see the previously typed times on the screen. But there will be lost if the power goes off even for a fraction of a second .it cannot be retrieve again. So, at the time of typing a program, the data are stored in the internal memory, which is known as primary memory. A primary memory is made from silicon semi-conductor materials, which consist of a large number of transistor etched on to silicon chips in high densities in semiconductor memory the transfer of information is much faster. However this semiconductor memories are volatile, this losing stored data when power is turned off the primary memory can be classified again into two main group, such as [a] ROM, and [b] RAM.

[a] ROM (Read Only Memory): - The full form of ROM is Read Only Memory. In this type of memory is a non-volatile memory. It is not accessible to user, and hence he cannot write anything into it. ROM in used to stone permanent program, which initialize computer program (system level), micro codes, supervisory program to control computer. This type of contents are written at the time of it is fabrication. There are different types of ROM. they are:

(a) PROM: - The full form of PROM is “Programmable Read Only Memory”, where data can be stored or write occasionally by special means.(b) EPROM: - The full form of which is “Erasable Programmable Read Only Memory”, where the existing stored program can also be stored by special means.(c) EPROM: - The full form of EPROM is “Electrically Erasable Programmable Read Only Memory”; it acts in similar manner as the EPROM. The only difference is that the exiting content can be erased with the use of electrical pulses.

[b] RAM (Random Access Memory): - RAM means random access memory and data currently being executed. It is a volatile memory. It a RAM any memory location can be accessed in a random way without going through any other location. The access time is same for each an every memory location. Since information can be written into or read from RAM’s, they are used as read or write memory of a computer system. When we typed a program or enter data into a computer through the keyboard or other external storage devices (like floppy disk, cd, hard disk etc) into the computers memory, it is actually stored in RAM temporarily at the time of execution of any program, it execute sequentially the stored instruction from RAM. There are two types of RAM- (i) Static RAM (SRAM) (ii) Dynamic RAM (DRAM).

*CACHE MEMORY AND REGISTERS: - Beside ROM and RAM there are some other primary memory like cache or buffer memory and different type of registers is a special

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type of fast access memory which is used in high speed computers to work or buffer and is placed between cpu and main memory in order to much faster than from ROM and RAM, there by reducing the time of execution of program. The cache is a high-speed memory but expensive hence smaller in size than other memories. Registers are temporary storage medium, which are used to store data or address temporarily. While it is flowing from one part to another part of computer. Some of the common registers MAR (Memory Address Register), MBR (Memory Buffer Register), MDR (Memory Data Registers), and I/O Register etc.

(ii) Secondary memory : -Secondary unit memory is those where the data can be stored and which will remain as it is even when the power is turned off. So this type of memory is called non-volatile memory. It is made by the magnetic materials and also called external /auxiliary memory .its storage capacity is much more than the primary memory and its cost is also very low than the main memory. Though the operating speed is low than the primary memory its low cost storage and high volume of storage capacity makes it widely used.

The total range of secondary storage is divided in two major groups. They are:

(a)Sequential access system and (b) Direct access system

(a) Sequential Access System (SAS) : -In sequential access system data can only be accessed sequentially. So, the data stored earlier has to be accessed first before data stored at the end cannot be accessed .we cannot access data from any position at the stored medium at any point of time. In earlier days proper tapes were used as the secondary storage medium. Nowadays magnetic tapes are very much suitable for storing a large amount of data.

(b) Direct Access System (DAS) : –The direct access system the data can be stored at the required position of the medium directly and can be accessed from any position of the medium the DAS takes less access time where as a sequential access system needs much longer time and is also dependant on the position of the data stored. In that day various types of magnetic disks are used for DAS, hard disks, floppy disks and compact disks are now very useful storage device for DAS.

(b) Arithmetical and Logic Unit (ALU): -

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This unit is used to perform all the arithmetic and logic operations such as addition, subtraction, multiplication, division, comparison e.g. for example, consider the addition of two numbers A and B. The Control Unit will select the number from its location in the memory and load it into the ALU. Then it will select the number B and add it to A in the arithmetic unit. The result will then be stored in the memory or retained in the arithmetic unit for further calculations.For such type of operations, there are some sets of registers (registers are circuits that store information temporarily, during the execution of instruction), and a special purpose register called accumulator, in the ALU. A set of logic gates and adder circuit are also resident members of the ALU.

(c) Control Unit (CU): -This unit coordinates the activities of all other units in the system. Its major functions are:1) The control unit retrieves data and instructions from the

memory.2) Issue commands to the various parts of the computer system

and initiates appropriate functions by the ALU.3) It controls and supervises the execution of the instructions in

order of their sequence.4) And it sends the results to the output devices.

The location of ALU and CU are performed in synchronism of a clock pulse,This is expressed as CPU speed. Modern computer’s CPU speed is expressed in terms of MHz (Megahertz) clock speed, which means the number of cycles per second that will be completed. C. Output Devices: - Output devices are units through which we get the output or result of any computer process. There are different types of output devices, which are used, in present days. These are: Visual Display Unit (VDU) which also known as Cathode Ray Tube (CRT), similar to the picture tube of the TV. And various types of printers, like dot martin printer, line printer, inkjet printer, laser printer and also CD, floppy, etc are the example of both input and output devices.

SOFTWARE:Computer need clear-cut instruction to tell them to do, how to do, and when to do. A set of instruction to carry out these functions is called program. A group of such program that is put into a computer to operate and control its activities is called the software. This program must reside in the internal memory to execute their instruction.

For example if we want to delete some data stored in memory, the system uses one set of program instructions.

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Software is an essential requirement of computer system, as a car cannot run with out fuel; a computer cannot work without software.These are two major kinds of software that are implemented as : (1) System software (2) Application software

System software: - System software consists of programs that manage and support computer system and its information processing activities. These programs serve as a virtual software interface between computer and the application programs of end user. The most important System software package for any computer is its operating system. An operating system is an integrated system of programs that manages the operation of CPU, controls the I/O and storage resources and activities of the computer system and provides various support service as computer executes the application programs of the users.

Application software :- It include a variety of programs that can be use for some specific purpose like Web browser, E mail, Word processing, Spreadsheet, DBMS, DTP, Accounting, Science and Engineering process.

FIRMWARWEThere are some programs, which are permanently coded instructions stored within the ROM and which are implemented within the Hardware. These are called Firmware, and they usually can not be change without changing the Hardware component themselves. The example of Firmware is ROM BIOS (Read Only Memory Basic Input Output System).

HUMENWARE The people who are involved in the operation and management of computer system are known as Humenware. The example of Humenware is the users of the computer, like hardware engineer, Software Engineer, Programmer, Operator etc.

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