Computer program
A computer program is usually stored as a file on the computer's hard drive. The file contains a list of instructions. When the user runs the program, the computer reads the file does what the instructions tell it to do. These instructions can be very simple, like "add these numbers together" or "save these letters". A computer program is written by a programmer, who combines many of these simple instructions to do complicated things, like talking to the computer's screen and telling it to show a video.