MFT & MVTMemory management is the functionality of an operating system which manages primary memory and moves processes back and forth between main memory and disk during execution. It:- Keeps track of each and every memory location. - Checks how much memory is to be allocated to processes. - Decides which process will get memory at what time. - Tracks whenever some memory gets freed or unallocated - And correspondingly it updates the status. In multiprogramming, multiple users can share the memory simultaneously. MFT and MVT are types of contiguous allocation multiprogramming. OS/360, officially known as IBM System/360 Operating System, is a discontinued batch processing operating system developed by IBM for their then-new System/360 mainframe computer. MFT and MVT are different Fragmentation: 1) Internal: Partial or Incomplete usage of a block of memory. can only get the memory. at the beginning there are no partitions. generated from the same tapes and sharing most of their code. Number. of blocks. MVT is a more ``efficient'' user of resources but is more difficult. Or we can bind address at the compile time. 2) External: Entire block of available memory cannot be used. MVT (Multiprogramming with a Variable number of Tasks) - - In MVT or variable partitioning scheme.variants of OS/360. So the processes whose memory requirement is equal to or less than 4KB. OS/360 MFT could run several programs but only after partitioning the memory required to run each. That is. let us consider that each block is of size 4KB and there are total 4 partitions. Each partition may have a different job queue or all partitions may share the same job queue(tasks). the partitioning of memory changes as jobs enter and leave. . memory devoted to it was inaccessible by other programs. Advantages: At the time of compilation only the address of each word can be given. Each job gets just the amount of memory it needs. it is not flexible because we cannot change the no. Partitioning can be done at the startup time and altered later on. There is only the OS area and the rest of the available RAM. Fig: Multiprogramming System MFT (Multiprogramming with a Fixed number of Tasks) - - Fixed number of jobs can be processed concurrently. size and location of partitions vary dynamically. User area of memory is divided into a number of fixed size partitions. The (real) memory is partitioned and a batch is assigned to a fixed partition. Number of jobs can vary. The memory assigned to a partition does not change. if one program was idle. Memory wastage is caused due to fragmentation. Disadvantages: Degree of multiprogramming is rigid. The memory is given to the processes as they arrive. its limitation was that. For example. OS/MVT was also able to allocate all of computer’s memory to a single large job. This method is more flexible as variable size process can be given memory. .- - OS/MVT allowed memory divisions to be re-created as needed. There is no size limitation. Disadvantages: It also suffers from external fragmentation. Whenever memory was available. In this scheme compile time address binding is not possible. Fig: Multiprogramming with variable number of tasks Advantages: In this scheme there is no internal fragmentation. the system searched a queue of jobs for any that could be run on available memory. creating a versatility unavailable in other operating systems.