Mr Arthur Clark in 'Readers' Input' in the July 1992 edition of Sixteen Bits wonders where his 40 KB goes when he runs DOS5's DOSSHELL.
I'll take a guess and say that he has the 'Enable Task Swapper' option enabled under the 'Options' menu. If he disables this option he will save over 37 Kb. Consulting the DOS5 program MEM with the /c switch reveals that enabling this option starts up an additional program -- DOSSWAP -- which uses 35 Kb and increases the resident size of DOSSHELL by over 2 Kb. In fact DOSSHELL normally swaps most of itself out of memory when running programs, leaving a tiny restart segment of only 2.2 Kb.
Unfortunately, the way DOS works means it also loads in another 3.1 Kb of COMMAND.COM on top, ignoring the COMMAND.COM already sitting there underneath DOSSHELL.
On my system without running DOSSHELL I have 618.2 Kb of conventional memory for running programs, with DOSSHELL I have 612.8 Kb. With DOSSHELL's task swapper working I only have 575.5 Kb.
Still, this isn't bad when you think of all the work the task swapper has to do, monitoring all keystrokes for the hotkeys that invoke it, copying all of conventional memory's contents to a temporary disk file and so on.
© 1992 - Stephen Dawson