Expanded memory

Expanded memory refers to the memory between 640K and 1MB that is usually unavailable to DOS. Using expanded memory managers, you can force DOS to load drivers in this area, thus freeing more of the lower 640 of conventional memory for use by programs. This applies only to running DOS programs under Windows.

For more information, see this article:

How to Increase Conventional Memory for MS-DOS-Based Programs

http://support.microsoft.com/support/kb/articles/Q134/3/99.asp

(Sometimeswhen I cut and paste URL's it looks ok to me but once the answer is posted, an extraneous space will have crept in. Make sure you delete any extraneous spaces or the page won't load).

Your question mentions EXTENDED memory and EXPANDED memory. These are two different things. EXPANDED memory refers to the Expanded Memory Specification or EMS. EXTENDED memory refers to Extended Memory Specification or XMS.

This Microsoft KBarticle, Overview of Memory-Management Functionality in MS-DOS, at
http://support.microsoft.com/support/kb/articles/q95/5/55.asp , gives info about the two.

to get at least 600KB memory:
edit config.sys and add 2 lines. the 1st one being your XMS driver (usually himem.sys) type device=(path)\(xms driver filename)
then the next line is the same except that the filename is your EMS driver. add NOEMS at the end if you need EMS or add RAM. Now add DOS=high,umb now you have 600KB base memory + extended memory.