It includes all physical components which are touchable and sensible. It is mainly divided into 4 parts CPU, input device, output device and auxiliary memory.
CPU is the Central Processing Unit, which contains electronics circuits and execute instructions and also controls the operations of other input output devices. CPU is again divided into three parts ALU, CU. and memory.
ALU (Arithmetic and Logical Unit) performs arithmetical operations like addition, subtraction, multiplication, division as well as logical operations like AND, OR,NOT operations.
CU (Control Unit) controls each and every activity of processing of all connected devices. It acts as a brain. Its main function is to fetch instructions from main memory and execute it. Normally it executes instructions sequentially. But again this depends on specified instructions.
Memory is also called as a main memory or primary memory or internal memory. It is mainly used to stere instructions or information in the form of zero’s and one’s. Control unit fetches instructions from the main memory.
This memory is also called as a semiconductor memory because it is constructed by the semiconductor material like silicon. This memory is again divided into various types that are RAM, ROM, PROM, EPROM EEPROM.
RAM (Random Access Memory) can hold data till power is on. So it is called as a volatile memory (that means temporary memory)
ROM (Read Only Memory) can hold data permanently. Ordinary user can not store his information into the ROM only manufacturer of the ROM chip can store data into it. It consist of programs which can control 1O devices (BIOS), booting procedures, programs of some mathematical functions like sin, cos, tan ete. So it is called as a non volatile memory (that means permanent memory)
PROM(Programmable Read Only Memory) can hold data permanently Programmer can store his information into the PROM but only once. After that modification is not allowed. So it is called as a non volatile memory (that means permanent memory).
EPROM (Erasable Programmable Read Only Memory) can hold data permanently. User can store his information into the EPROM but only once. After that bit modification is not allowed. User can delete all the contents of the chip using ultra violet rays and again rewrite information on the EPROM chip. So it is called as a non volatile memory (that means permanent memory)
EEPROM (Electrically Erasable Programmable Read Only Memory) can hold data permanently. User can store his information into the EEPROM and bit modification is allowed. So it is called as a non volatile memory (that means permanent memory). But till now it is not used as a secondary memory because of its cost.
CPU ecepts information from user through input device. There are many input devices like keyboard, amouse, mice, tracker ball, touch screens etc.
CPU conveys information to user through output device. There are many output devices like monitor, LCD, printers, plotters, speakers etc.
Auxiliary memory is also called as a secondary memory or external memory or magnetic memory. This is permanent memory. User can store data (programs or documents or pictures etc.) permanently on this type of memory. It can be modified. There are many types of secondary memory That are hard disk, floppy disk, CDROM. pen drive etc..