Multi programming

Multiprogramming is a technique for handling two or more independant program simultaneously by overlapping or interleaving their execution or by loading them into primary storage and executing their instractions concurrently. The overlapping or interleaving os executions of programs is usually controlled bu and Operating system which attempts to optimize the overall performance of system in accordance with the priority requirements of the various jobs. These systems operates on the basis of I/O interrupt concept.They use two distictive functional units.One is Control Unit and other is I/O Control Unit having direct access to memory.Computer can execute several programs by rotation or by priority. It takes up program one for procesing and continues it till an i/o operating is encountered,then the control is transfarred to the i/o ontrol unit.The ontrol unit now takes up program two and continues in same manner with additional programs. The execution os the first program will be resumed when its i/o operatin is completed. Such a computer can execute a one program at a time.However since the switch over is accomplished very fast that the user feels that all programs are runnung concurrently.