Multitasking -  Single Processor Many Users Many  Tasks

In multitasking or also  called  time sharing  systems  multi  user  more than  one users are sharing  one processor  at a time. This type of systems is shown in figure  several dumb terminals  without  processor are connected to a powerful  computer usually mini or mainframe through wires if in the same office or telephone line. The  speed of user is much slower as compared to the computer. Hence  the computer can server many users on the timesharing basis. Computer  works  on the  program  of the 1^st  user   for  suppose 20 milliseconds then works on 2^nd  user program of r 20  ms then processes on 3^rd  user program for next  20 ms  and so on and then comes back to the 1  user program in few ms after serving all the user and the cycle is repeated. Each user in the system  feels that he is the only user using the computer. Ticket reservation systems  may be an example  of such  systems.

The  drawbacks of  systems are:

A. If the  computer  has nay  problem  and not  working  the whole  systems will  crush to halt.

B. .As the number  of users  of increase time taken to complete one cycle to responding all uses also  increases. People  will have  to wait  for their  turn.