Bug

A software bug is a design flaw in a program that produces an incorrect or unexpected result. The severity of these malfunctions is very variable, the bug can cause a simple display error as well as a total system crash.

Thus, a bug can be qualified at different scales : minor, major or critical. As the name suggests, a minor bug will be of little inconvenience to the application and easily circumvented by its users, a major bug will significantly deteriorate its functionality while a critical one will completely block its use.

Bugs are classified into 3 main types :

• syntax errors, caused by the incorrect use of a predefined syntax
• runtime errors, often related to a corrupted registry, an incomplete installation or missing files
• logic errors, related to the use of logic operators and comparison operators

However, a bug is just one type of problem that a program can encounter : it can also work without bugs and yet be difficult to use and frequently fail.