Computer System



A Computer is a programmable machine which stores data or information, process data and provide us necessary information.

Computer consists of hardware and software. The actual machinery wires, transistors and circuits are called hardware: the set of instructions and data are called software. These parts of the computer work together to perform the tasks given by the user. Suppose you want to print a document and when you give instructions to print, the CPU with the help of operating system sends instructions to a printer. The printer follows the instructions and starts printing task. So, such a system in which computer hardware and software work together to fulfill the purpose of the instructions or programs is known as computer system. In other words, a computer system is a set of hardware and software, which processes data in a meaningful way. The hardware components of computer system are:

1. Input Unit
2. Central Processing Unit
3. Output Unit
4. Auxiliary / Secondary storage



Building block of PC
1. Input Unit

Data and instruction in the human understandable form are entered through the input device like keyboard and it converts them into computer understandable form and passes to the memory unit (RAM).

Input devices are those devices through which we can input data to the computer. They convert the data and information into the form understandable by the computer. Some of the input devices are: Mouse, Keyboard, Touch Screen, Digitizing Tablet, Track Pad, Track Ball, Light Pen, Joystick, Scanners etc.

An input unit performs the following functions:
a. Input unit accepts or reads the data and instructions from the user.
b. Input unit converts these inputs in the computer acceptable form i.e. binary code.
c. Input unit supplies the converted inputs to the computer system for further processing which are stored temporarily in RAM.

When you want to use data, instructions or programs stored in a secondary storage, they are also transferred from the secondary storage like hard disk, compact disk or pen drive to the memory unit.

2. Central Processing Unit


The central processing unit (CPU) is the brain of the computer system. Central processing unit works with operating system and executes a set of instruction and controls different peripheral devices by sending and receiving control signals. The CPU also controls the flow of data by directing the data to enter the system, placing data in the memory, sending the data to ALU for the processing and directing the output of information.


3. Output Unit


The results of processing in the memory until are directed to output unit. The output unit shows them and other information to the user in the human understandable language. The output unit performed the following functions.

a) Output unit accepts the result produced by the computer which is in binary form.

b) Output unit converts binary form of results to human understandable form.

c) Output unit shows the converted results to the user.

Output devices are those devices that convert processed data or results into a user understandable form. Examples of output devices are: printers, plotters, monitors, multimedia projector, etc.


4. Secondary Storage


The secondary storage stores data, information, files and programs permanently. A computer can only access the data and programs stored in the primary memory directly. So, to use the files, programs or data stored in the secondary storage need to be transferred into the memory unit. The transferring of a program from the secondary storage to the computer memory is known as loading a program. The processed data and programs that are needed for the future uses are stored in the secondary storage like hard disk, compact disk and digital video disk.



Memory unit

Memory unit is the device in which computer stores its actual data. If we put data from input devices, these data are stored in to the computers memory in binary form i.e. 1’s and 0’s. If we need that stored data, computer reads the data from its memory and provides us through output devices. These memories are RAM, ROM and storage devices are Punched Cards, Magnetic Tape, Hard Disk, Floppy Disk, Zip Disk etc.



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