#Reimage computer free#
Some systems allow partitions to be swapped out to secondary storage to free additional memory. Compaction moves "in-use" areas of memory to eliminate "holes" or unused areas of memory caused by process termination in order to create larger contiguous free areas. Relocatable partitions are able to be compacted to provide larger chunks of contiguous physical memory. Partitions may be relocatable using hardware typed memory, like the Burroughs Corporation B5500, or base and bounds registers like the PDP-10 or GE-635. MVT and successors use the term region to distinguish dynamic partitions from static ones in other systems. IBM System/360 Operating System Multiprogramming with a Fixed Number of Tasks (MFT) is an example of static partitioning, and Multiprogramming with a Variable Number of Tasks (MVT) is an example of dynamic. Partitions may be either static, that is defined at Initial Program Load (IPL) or boot time or by the computer operator, or dynamic, that is, automatically created for a specific job. The system took advantage of memory interleaving to place what were called the i bank and d bank in separate memory modules. The UNIVAC 1108 Storage Limits Register had separate base/bound sets for instructions and data. Other systems used base and bounds registers which contained the limits of the partition and flagged invalid accesses. The IBM System/360 used a lock-and-key technique. Partitioned allocation usually requires some hardware support to prevent the jobs from interfering with one another or with the operating system. Memory management consists of allocating a partition to a job when it starts and unallocating it when the job ends. Each partition might contain all the information for a specific job or task. Partitioned allocation divides primary memory into multiple memory partitions, usually contiguous areas of memory. Early versions of the MUSIC operating system used this technique. An embedded system running a single application might also use this technique.Ī system using single contiguous allocation may still multitask by swapping the contents of memory to switch among users. MS-DOS is an example of a system which allocates memory in this way. All the computer's memory, usually with the exception of a small portion reserved for the operating system, is available to the single application. Single allocation is the simplest memory management technique. Memory management techniques Single contiguous allocation
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