KEY BOARD, MONITOR, CPU

KEY BOARD

The keyboard is one of the most useful input device. It provides a convenient way to feed data instructions into a computer. A computer keyboard is similar to an electric typewriter keyboard with slight modification having additional keys for specific functions. It can be easily plugged with computer. Its main function is to enable the user to communicate with the computer.

MONITOR

The monitor is the name commonly used for the visual display unit. It is the most useful output device through which a computer communicates with the user. A video monitor has a TV like screen, which displays both alphanumeric characters and graphics. It has rapidly become one of the most popular methods of displaying data/information.

C.P.U

The Control Unit is the most important part of the C.P.U as it controls and coordincates the activities of all other computer units. It performs this function by issuing necessary commands to various components of the computer. It also controls the input/output devices as well as the backing storage devices. Another aspect of the control function of the CPU is governed by the programme. A programme is a set of instructions in a sequence, which tells the computer what to do. The programme, written to solve a specific problem, instructs the computer system to perform mathematical calculations, input data, store data, display results on a visual device and so on. The flow of instructions, data and results is governed by the Control Unit, which sets the various logic gates, feeds the numerical data and provides the clock pulsees (heart beat of the computer) that regulates the speed of all the operations. Instructions received from input unit are stored in one part of the memory, while data is stored in another part. The Control Unit generates signals in accordance with the programme, the control signal or the control input provides a desired sequence of arithmetic operation and retrieves the numerical data from the memory.

COMPUER STORAGE

Computer storage also referred, as computer memory is actually an electronic file in which instructions and data are placed until needed. Computer storage is divided into two classes:

• Main storage or Main memory
• Secondary storage or Secondary memory

The major reason for the distinction between main and auxiliary storage is the cost in relation to performance and capacity. Main memory provides very fast performance or it is directly accessible by the CPU but is much more costly per unit of capacity than the auxiliary storage devices. Auxiliary storage provides maximum capacity for large data files.



MAIN MEMORY

Main memory is the computer's primary storage. It is an extension of the Central Processing Unit (CPU) and is directly accessible to it. Its function is controlled by the Control Unit, which sends READ or WRITE signal for the appropriate memory location. Main memory accepts data and instructions from the input unit, exchanges data with and supplies instructions to other parts of the Central Processing Unit (CPU). The memory unit also stores those instructions and data that are currently being used by the CPU or those instructions and data awaiting immediate execution. Its capacity must be sufficient to retain both the usable amount of data and instructins needed for processing it. Some operations require more instructins or data than can be held in main memory at one time. In such cases, main memory is supplemented with secondary storage. The capacity of a storage device is expressed as number of bits, characters or bytes. One byte is a group of eight bits that forms one character. A bit is a binary number used in digital computers, which stands for binary digit. One bit contains the minimum information and is a basic unit that has value 0 or 1. Thus if the memory of a computer is 32000 bytes, it means that it can store 32000 characters. Semiconductor storage (integrated circuits) and magnetic cores are the most widely used forms of main storage. Besides reduced size and increased speed, semiconductor storage offers the advantage of non-destructive read. There are vaious storage types available, which included RAM,ROM,PROM,EPROM, and EAROM. The most common kind of semiconductor storage is RAM (Random Access Memory) and ROM (Read only Memory).

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