Up-Up-Down-Down-Left-Right-Left-Right B, A, Start.

In the 80s, Konami of America and Japan released many games for the Nintendo Entertainment System. Traditionally, programmers would program in hidden 'cheat codes' to help make gameplay easier, which aided especially during late testing periods before commercial launch.

Konami released many popular games on the NES during this era, such as Gradius, Life Force, and Contra. These titles, as well as many subsequent ones, used the same cheat code listed above. Because of it's reoccurence, it became known as 'The Konami Code', and knowing it by heart is one of the trademark signs of a true, old-school gamer.

A common alteration on this code is:
Up-Up-Down-Down-Left-Right-Left-Right, B, A, SELECT, Start.

Many people mentally add in a 'select' in there for one reason only--on the menu screen, pressing select changed the cursor to '2 players' instead of '1 player'. Contra was always more fun to play with a friend.

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Up, Up, Down, Down, Left, Right, Left, Right, B, A, Start. A cheat code common to most classic Konami games, which gave the code its nickname. The code itself has become a symbol of old-school and/or arcade gaming. Punk group "The Ataris" named a song after the code on their album, "End Is Forever." Ironically, the Konami Code never made an appearance on an Atari console.

^^vv<><>ba Start - The famous code used in many Konami games. Became famous because of Contra.

up up down down left right left right b a start

A popular cheat code in MANY Konami games. Often helps the player immensely except for Gradius III.

The code that every Nintendo nerd had burned into their brain during the late 80's and early 90's. (up-up-down-down-left-right-left-right-B-A-START)

Same as below, but the phrase can also be used figuratively and/or metaphorically.