In speaking of computer applications, an error is a mistake or discrepancy in the execution of a program or in a file or calculation. A computing error can be caused by several factors. One is operator or user error. For example, if a user accesses the "Paste" command when nothing has been copied, this would be an example of a user error that could happen in any program at any time. Other errors that occur involve the software itself. Two important classes of errors are the compile-time-error and the run-time error.
A compile-time error happens as the program is being compiled, that is, in the process of the source code becoming an executable program. Run-time is the execution of a computer program, as opposed to installing, loading, or exiting the program. A run-time error is a glitch, bug, or problem that arises as a program is being executed on a particular computer at a particular time. Many errors are caught in static software testing when a program is compiled — if it is compiled. Catching run-time errors is a key focus of dynamic testing of software.
In diagnosing a run-time error, it is essential to consider the run-time environment. The run-time environment is a similar concept to the operating environment. It refers to the hardware and software configuration under which the run-time error occurred or occurs, if it is reproducible. The run-time environment includes factors such as the operating system on the computer, the type of CPU (Central Processing Unit), as well as system software or run-time engines that the application draws on and requires to run properly.
Various types of run-time errors can arise while using a program. Some of them are user errors, such as failing to connect or turn on a peripheral advice or giving an invalid instruction, like "Paste" when nothing has been copied. Missing resources is another situation that can cause a run-time error. A computer virus or a memory issue can also cause a run-time error, as can a conflict with another program.