Multiprogramming with Fixed partitions This method allows multiple processes to execute simultaneously. Here memory is divided into fixed sized partitions. Size can be equal or unequal for different partitions. Generally unequal partitions are used for better utilizations. Each partition can accommodate exactly one process, means only single process can be placed in one partition. The partition boundaries are not movable. Whenever any program needs to be loaded in memory, a free partition big enough to hold the program is found. This partition will be allocated to that program or process. If there is no free partition available of required size, then the process needs to wait. Such process will be put in a queue. There are two ways to maintain queue Using multiple Input Queues. Using single Input Queue. The disadvantage of sorting the incoming jobs into separate queues becomes apparent when the queue for a large partition is empty but the queue for a small partition is full, as is the case for partitions 1 and 3 in given Fig. Here small jobs have to wait to get into memory, even though plenty of memory is free. An alternative organization is to maintain a single queue as in Fig. 5-1(b). Whenever a partition becomes free, the job closest to the front of the queue that fits in it could be loaded into the empty partition and run.
