Memory segmentation is an working system memory administration technique of dividing a pc's major memory into segments or sections. In a pc system using segmentation, a reference to a memory location contains a worth that identifies a phase and an offset (memory location) inside that phase. Segments or sections are also used in object information of compiled applications when they're linked together into a program picture and when the picture is loaded into memory. Segments could also be created for program modules, or for lessons of memory usage such as code segments and knowledge segments. Sure segments may be shared between applications. Segmentation was originally invented as a technique by which system software program could isolate software program processes (duties) and information they're utilizing. It was meant to increase reliability of the programs working multiple processes concurrently. In a system utilizing segmentation, pc memory addresses consist of a phase id and an offset throughout the section.

A hardware memory administration unit (MMU) is liable for translating the phase and offset into a physical address, and for performing checks to make sure the translation could be carried out and that the reference to that section and offset is permitted. Every section has a size and Memory Wave set of permissions (for instance, read, MemoryWave Community write, execute) associated with it. A process is only allowed to make a reference into a phase if the type of reference is allowed by the permissions, and Memory Wave if the offset throughout the segment is within the vary specified by the length of the section. In any other case, a hardware exception resembling a segmentation fault is raised. Segments could also be used to implement digital memory. On this case each phase has an associated flag indicating whether it's current in foremost memory or not. If a phase is accessed that is not current in important memory, an exception is raised, and the operating system will learn the segment into memory from secondary storage.

Segmentation is one methodology of implementing memory protection. Paging is another, and they are often combined. The scale of a memory phase is mostly not fastened and may be as small as a single byte. Segmentation has been carried out several ways on numerous hardware, with or without paging. Intel x86 memory segmentation does not match either model and is discussed separately beneath, and likewise in larger element in a separate article. Related to every section is data that indicates where the phase is located in memory- the phase base. When a program references a memory location, the offset is added to the segment base to generate a physical memory deal with. An implementation of virtual memory on a system using segmentation without paging requires that total segments be swapped again and forth between main memory and secondary storage. When a phase is swapped in, the operating system has to allocate sufficient contiguous free memory to hold all the phase. Often memory fragmentation results if there shouldn't be sufficient contiguous memory although there could also be sufficient in total.

As a substitute of a memory location, the section data includes the tackle of a page table for the segment. When a program references a memory location the offset is translated to a memory handle using the web page desk. A phase could be extended by allocating one other memory page and adding it to the segment's page desk. An implementation of virtual memory on a system utilizing segmentation with paging normally only moves individual pages back and forth between primary memory and secondary storage, just like a paged non-segmented system. Pages of the section may be located wherever in most important memory and need not be contiguous. This usually leads to a reduced amount of enter/output between main and secondary storage and lowered memory fragmentation. The B5000 is geared up with a section information table called this system Reference Table (PRT) which is used to point whether or not the corresponding segment resides in the main memory, to maintain the bottom handle and the scale of the section.

The later B6500 laptop additionally carried out segmentation