3.3.1d Memory Management

[3.3.1d MEMORY MANAGEMENT]

A problem common with job loading is that eventually main memory can become very segmented as jobs are coming in and being completed whilst others are still executing. Eventually there will be a point where a lot of main memory is segmented and a larger job cannot fit in at once.

A solution to this memory management problem is called paging.

Paging: Main memory is divided up into pages, each page is of the same size and from here each page is labeled and indexed. Therefore when a job enters, it may span a number of pages and this job can easily be found using the index table.

Another solution to this is called segmentation.

Segmentation: Segmentation frees up different sized blocks in main memory for the exact size (plus some overhead) of the job so that no space is wasted. Similar to paging however paging can waste space if a job doesn’t use the entirety of the page.

The advantages of paging…