What is bug computer?

A bug is an unintended operation of a computer program. Computers nearly always "Do what I say", but they may fail to "Do what I mean". Thus, most bugs are the fault of the programmer or system architect, not the computer.

An unintended operation can occur anyway when an unforseen input was not considered by the programmer or architect. Often, the complexity of a computer model may make it difficult for the programmer or architect to anticipate all possible states or inputs. Various design principles are aimed at reducing complexity and eliminating common types of bugs.

A "soft bug" is a functionality that was actually intended by the system analyst, but which is seems incorrect or puzzling to the end-user. In this case, the fault lies with the system analyst, rather than the programmer.

According to computer folklore, the term "bug" originated from an actual insect interfering with the computing hardware. While there were actual cases of this, the term "bug" in this sense predates computers.