Memory Management

Memory Management

1. One of the key roles of the OS is the management of memory

   • The OS needs to ensure that:
     • Memory is used efficiently - programs that are being used need to be sored in memory without space being wasted
     • Data in memory is secure - programs should not have access to other programs' data

2. Storing complete programs as a single block of memory is wasteful

   • It means that parts for the program not being used are taking up memory
     • And as programs are added and removed space can be used ineffciently
       • Items in memory are split up via paging and segmentaion

3. RAM is more expensive than secondary storage

   • A computer will have hundreds of times more secondary storage than RAM
     • When a system is running low on RAM it is able to use an area of the hard disk as virtual memory
       • Virtual memory is the use of secondary storage as an extension of a computer's physical memory
         • When a computer swaps pages back and forth too often the computer slows down. This is called disk thrashing

4. Paging is where programs are divided into equal sized blocks

5. Segmentation is where programs are divided logically, split into blocks containing modules or routines