The persistance of DOS

by Alan Zisman (c) 1997. First published in Computer Player, April 1997

If you believe the hype, Windows 95 can forget about DOS. Like a lot of advertising hype it's absolutely true. Part of the time.

Windows 95 does a good job of insulating its users from 1980s-era DOS limitations like the 640 kb memory dead-end and work-around memory management schemes. Or from having to fiddle with the Config.sys and Autoexec.bat startup files. And a lot of the time, it actually works as advertised, allowing users to simply start up a DOS program, and have it run (something that was much less often possible with Windows 3.1)

But while DOS may be buried, it's not quite dead, yet. Despite Microsoft's efforts to convince us that Windows 95 is the present and future of software development, many game developers are not quite convinced. They've grown accustomed to the power they had, under DOS, to directly access the computer's hardware-squeezing out the best possible performance for their games.

While many popular games are still being written for DOS, most are running properly in a Windows 95 DOS session. And that's nice for users-it means that these games can take advantage of Win95's CD-ROM, sound, video, and mouse drivers. In those cases, users don't have to mess with the DOS dirty work.

But many users want to keep playing their old DOS games on their new computers or under their upgraded operating system. Or they just bought a new copy of a classic game, perhaps re-released at a bargain price. And these golden oldies often won't be so happy sharing the computer with Windows 95.

All is not lost, however. Win 95 allows users considerable flexibility in setting up DOS sessions-far more than Windows 3.1 ever did. (Yes, OS/2 fans-not as much as that infinitely flexible operating system permits).

Here are a few tricks that should let you run almost every DOS program under Win95 without having to resort to clumsy workarounds like customized boot floppies.

* Increase the amount of ram in your default DOS sessions.

Win95 lets you run a computer without needing the DOS startup files, Config.sys and Autoexec.bat. In doing so, however, it doesn't optimize your computer's DOS sessions. Find out how much free DOS memory you have by starting up an MS-DOS window, and typing MEM. (Yes, press Enter). If you have less than 600 kb or so free, some DOS games will refuse to run.

You can increase the amount of free conventional (DOS) memory with a little fussing around with your Config.sys file. Start up Notepad (from the Start Menu's Programs/Accessories submenu), and open C:\Config.sys... if you don't find one, make a new file. Make sure it has the following three lines:

Device=C:\Windows\Himem.sys
Device=C:\Windows\Emm386.exe noems
DOS=high,umb

Save the file, shutdown and restart. Open a DOS session, type MEM again, and see how much free memory you've gained. It may still not be enough-in that case, you will have to check deeper into the workings of your DOS startup files.

* Are you loading unneeded DOS drivers in Config.sys and Autoexec.bat?

If you've upgraded from an older DOS/Windows setup, you may be loading unneeded DOS drivers, particularly for your CD-ROM, sound card, and mouse. Open your Config.sys file again-check it for additional lines starting 'Device=' or 'Devicehigh='. These are loading device drivers-software enabling your system to work with hardware add-ons. In most cases, these are not needed, as Windows 95 provides drivers for most hardware devices that don't use up your precious DOS memory.

If you find such statements (besides the Himem.sys and Emm386.exe statements previously listed), don't delete the lines. Instead, 'comment them out' by typing 'Rem' and a space at the front of each line. Save thefile. Similarly, open C:\Autoexec.bat in Notepad. Check for lines loading what seem to be Mouse or other hardware drivers. (You can ignore any lines starting with the word 'Set'). Comment them out the same way. Save, and restart your system. Check and see if your hardware-CD-ROM, sound card, mouse, and so forth are working properly. If so, you don't need those DOS drivers. But don't delete those lines just yet-you're going to need them!

Open a DOS session, and type MEM one more time. At this point, you should have at least 605 kb free conventional memory, which should be enough for most DOS programs.

This is a good start, but you may not be done yet. In next month's column, we'll look at what to do if your programs insist on EMS (expanded memory) or need to run in Win95's special MSDOS Mode.