In software, a bug is an error in coding or logic that causes a program to malfunction (出故障)or to produce incorrect results. Minor bugs—for example, a cursor(光标) that does not behave as expected—can be inconvenient or frustrating(有挫折的), but not damaging to information. More severe bugs can cause a program to “hang” (stop responding to commands) and might leave the user with no alternative(用户别无选择) but to restart the program, losing any previous(先前的) work that has not been saved. In either case, the programmer must find and correct the error by the process known as debugging(调试). Because of the potential risk to important data, commercial application programs are tested and debugged as completely as possible before release. Minor bugs found after the program becomes available are corrected in the next update; more severe bugs can sometimes be fixed (修补、修订)with special software, called patches, that circumvents (规避) the problem or otherwise alleviates (减轻) its effects.