A computer system comprises of an input unit, output unit, CPU and storage unit. An input unit accepts instructions and data from the user with the help of input devices such as keyboard, mouse, light pen etc. An output device is an electromechanical device, which converts machine-readable information into human-readable form. A computer memory is used to store information in the computer system.
Computer memory is classified into two broad categories primary memory and secondary memory. Primary memory is the internal memory that allows the computer to store data for immediate manipulation and to keep track of what is currently being processed by the CPU. Primary memory is of two types: Read Only Memory (ROM) and Random Access Memory (ROM). Secondary memory allows permanent storage of data and instructions. It includes devices like hard disks, floppy disks, CDs, magnetic tapes, pen drives and so on. The processor is a small chip that resides in a computer system. Its basic job is to receive input and provide the appropriate output.