(A) CENTRAL PROCESSING UNIT: CPU controls the entire working of a computer. It is the CPU which processes the data according to the program or commands given to it and outputs the result.
The 3 major subunits of CPU are as follows:
(1).The control unit; It fetches, decodes, executes the commands or program instrutions.it controls the flow of data between its internal memory registers, the ALU and other parts of the computer system.
(2).The memory unit: It registers stored the instructions and the data that is currently being processed by the CPU
(3)The Arithmetic and logic unit (ALU); The performs the arithmetic operations and logic operation on the data fetched from registers of the memory unit and writes the result back onto the registers for temporary storage. The control unit then transfers the result to an external memory device for storage or to an output device.
(B).INPUT DEVICES: An input device allows a user to communicate with a computer. it is used to give instructions or read data and program into the computer. It also converts the instructions and data into machine readable form which the computer can understand. eg. keyboard, mouse, scanners, webcamera, microphone barcode reader etc
(C).OUTPUT DEVICES: An out put device is used to convert the digitized information output of the CPU into a form that can be understood by us.
Eg. monitor, printers, speakers etc.
(D).STORAGE DEVICES: A memory or storage device, outside the CPU is used to store date and program instructions for a short term or long term is called memory. These are classified into (a) primary (b) secondary memory
(a).primary memory: This is a short term memory which temporarily holds the programs instructions and data that the CPU can immediately access while processing .eg. RAM. IS VOLATILE
(b).secondary memory: This is long term memory which is used to permanently store raw and processed data, and programs. it is also called as a backing store , since it contents are held for reference and not for immediate execution by CPU. eg. HARD DISK(CD),PENDRIVE,DVD,
IT IS NON-VOLATILE.