DOS Games Dilemma - Part One
This week's article looks at setting up DOS programs (typically games) to run under Windows 95 with information about such things as virtual drivers, memory settings and using PIF's - Program Information Files.
What's the problem?
DOS programs and in particular - DOS games tend to use the very limits of a PC's power. They often do this by accessing hardware directly rather than through the operating system. Every ounce of speed is used by using the direct approach.
However, this direct approach causes Windows so many problems. Windows, by its' very nature requires programs to 'talk' to the computer through Windows itself. This is done by the programmer using code that is supplied by Windows rather than routines written by the programmers themselves.
For example, to draw a shape on a screen, Windows has drawing routines that do this for you. Indeed, a window and its' components (such as title bar, buttons, slider controls), are handled by Windows so that the programmer does not need to write code to draw these objects.
This is fine for most sedentary programs like word processors, databases and the like but not so useful when you want screaming fast graphics flying around the screen with suitable sound effects!
There appears to be a stalemate here and this often causes problems running DOS programs under windows.
Another problem is the age-old DOS 640KB limit. This limit, imposed when DOS was first written in the early 1980's said that the maximum base memory a program could use was 640KB. In those days, a BIG computer was 64KB so multiplying that by 10 would be more than enough room. How wrong they were!
Into this 640KB must go the program itself along with driver programs that are used to communicate with the hardware itself.
This may seem a daft way of doing things but in fact - it paved the way for the PC industry. It allowed third party hardware components to be added to a PC without having to replace the entire computer. Try fitting a printer to a dedicated computer like hand held game consoles!
How does Windows handle this?
Windows 3.x handled DOS programs by allowing the user (and yes - it was usually left to the user!), the ability to create a 'safe environment' in which the DOS program could run in - completely oblivious to Windows. This is known as a shell.
A Program Information File (PIF) was used to set up this environment. It included such things as command line parameters, the type of available memory and whether the program could run in a window.
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