In WarGames (1983), David Lightman discovers that the password for accessing the WOPR system is Joshua.
David finds the password while investigating Stephen Falken, the computer scientist who designed WOPR. He realizes that Falken named the system after his deceased son, Joshua, and that the name is also used as the access password.
WOPR, short for War Operation Plan Response, is the fictional military computer that David accidentally connects to through a back door. The machine interprets his simulated game of Global Thermonuclear War as a real attack.
A common mix-up is confusing Joshua with the name of the game David initially selects. Joshua is the password and also the name associated with Falken’s son and WOPR’s artificial intelligence.