Cheat Code
Most of the available cheats for "X-COM: UFO Defense" don't rely on actual codes, but one cheat code exists for skipping the current level being played. Starting at the Battlescape screen, the player can hit "Ctrl C" or "Ctrl G," completing the level and carrying over the results from the previous level.
Extra Hints
To manufacture for free, the player can choose an item to be manufactured but assign no engineers to it by leaving the number to create at "0" and returning to the base management screen. Once you go back into manufacturing, you can assign any number of engineers, but only manufacture one item, which costs you nothing.
File Copying
Some cheats for "X-COM: UFO Defense" require copying files into different games, to gain knowledge achieved in previously saved games and start a new game with extra skills and abilities. To start, you must enter the game directory, and select the game from the most advanced available saved game slot. Accessing the files "research.dat," "product.dat," "facil.dat" and "up.dat" from the game and copying them into a new saved game, lets you use alien weaponry and craft right away. By copying other files, such as "soldier.dat" and "craft.dat," you can power up soldiers and obtain secret transportation abilities.
Warning
Advancing your game by copying files does pose the risk of corrupting your game or causing it to crash. To prevent corruption when copying the "soldier.dat" file, you must make sure the number of soldiers from the old file equals the number of soldiers in the new file. Also, the "craft.dat" file is less likely to be corrupt when you have two fighters and one skyranger in the hangars. If alien UFOs are in sight, that could corrupt a copied file.