DOS 4 GW: Difference between revisions
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A popular DOS extender from the early 90's. Back then, most advanced PC OSes, such as Microsoft Windows, OS/2 or various flavors of [[UNIX]], didn't allow the programmer full direct access to the hardware, something a lot of game developers relied on for performance-enhancing tricks. Their own [[API |
A popular DOS extender from the early 90's. Back then, most advanced PC OSes, such as Microsoft Windows, OS/2 or various flavors of [[UNIX]], didn't allow the programmer full direct access to the hardware, something a lot of game developers relied on for performance-enhancing tricks. Their own [[API]]s were generally suited to the needs of [[Serious Business|more serious applications]], not video games. That left a PC programmer with MS-DOS as a system of last resort, as it ''did'' allow direct access to hardware, but then another problem reared its ugly head: the infamous 640K barrier. |
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Due to the way the PC's memory was laid out, the maximum amount of memory available for user programs in DOS was just 640 kilobytes; most of the time, even less was available, since DOS itself and device drivers like HIMEM and EMM386 used some RAM as well. Most PCs of the time routinely sported several megabytes of RAM, but DOS couldn't use it because it ran in something called "real mode", where only the first megabyte of RAM is visible. To add insult to injury, DOS was not a multitasking OS and had no support for multithreading or multiple processes running at once; while there were tricks available to fake it, like the "Terminate and Stay Resident" system call, they were unreliable and not terribly useful in a gaming environment. In short, many games under DOS ended up implementing their own OS to make up for DOS's shortcomings. |
Due to the way the PC's memory was laid out, the maximum amount of memory available for user programs in DOS was just 640 kilobytes; most of the time, even less was available, since DOS itself and device drivers like HIMEM and EMM386 used some RAM as well. Most PCs of the time routinely sported several megabytes of RAM, but DOS couldn't use it because it ran in something called "real mode", where only the first megabyte of RAM is visible. To add insult to injury, DOS was not a multitasking OS and had no support for multithreading or multiple processes running at once; while there were tricks available to fake it, like the "Terminate and Stay Resident" system call, they were unreliable and not terribly useful in a gaming environment. In short, many games under DOS ended up implementing their own OS to make up for DOS's shortcomings. |
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