HIMEM.SYS. Mean anything to you? What about CONFIG.SYS? PC gaming used to come with a very severe limitation and that was the now pathetic total of 640KB of RAM. That was conventional memory and, for the uninitiated, 640 kilobytes is about the same size of that amusing picture of an angry cat that was probably just posted to your Facebook feed. But in the old days it was the basic limit of non-extended PC memory and many, many games absolutely insisted on ALL of it. It didn't matter if you had purchased extended RAM to increase the capacity, the core game had to a squeeze into that tiny block like a fat guy in a little coat. So PC gamers would write a custom boot-up batch routines that would remove nonessential memory-hogging programs for each and every game. Disable the mouse, turn off the localised keyboard, fiddle with the sound card etc. This process would sometimes take hours, but the player would do anything just to squeeze enough bytes to run Wolfenstein. Imagine buying an Xbox One and instead of navigating to the desired game on the dashboard and hitting A to play, you had jailbreak it and literally rewrite the start up procedure of the entire console. Not only that, in doing so you'd probably break other games and possibly brick your system permanently. Each change you made risked the system's integrity especially when messing in the BIOS prodding at the IRQs. At best you played the game in all it's glory. At worst you knackered your IBM PC compatible. Sweet!.
A Welsh semi-retired television producer and actor known for low end work that astonishingly people actually watched and even garnered some awards. Originally residing in the electrically-challenged Amish areas of Pennsylvania he has written a few books (Hollywood Pants and Hollywood Horrible Hints and Terribly Fake Tips vols 1 & 2) which you can buy on amazon and all great book stores.
After a brief stint in Australia he now finds himself back in the Welsh valleys of his home country noting that it hasn't changed a bit!