"From The Texas Instruments TI-99/4A was an early home computer, released in June 1981, originally at a price of USD $525. It was an enhanced version of the less-successful—and quite rare—TI-99/4 model, which was released in late 1979 at a price of $1,150. The TI-99/4A added an additional graphics mode, "lowercase" characters consisting of small capitals, and a full travel keyboard. Its predecessor, the TI-99/4, featured a calculator-style chiclet keyboard and a unique style of ASCII that lacked lowercase text.
Some of the most popular TI-99/4A games included Parsec, TI Invaders, Munch Man, Alpiner, Tombstone City: 21st Century, and Car Wars.
Many TI-developed video games, especially those developed by John Phillips, may be forced into "cheat mode" by holding the shift key and pressing 838. Terse messages often appear, which may allow the user to move to a different round of the game. In Munch Man, the top screen and top round includes invisible Hoonoos ("ghosts" in this blatant Pac-Man derivative) which travel several times faster than Munch Man. In Alpiner, the player can select which mountain to climb. 838 (with or without SHIFT) in Star Trek gives a random but high level of torpedoes, phaser power, and warp drive energy."
Source: Wikipedia, "TI99", available under the CC-BY-SA License.