We often hear the 【21】______ 'Bug' while using computers. But what is a bug? In computer science, a bug 【22】______ an error in software or hardware. In software, a bug is an error in coding or logic that causes a program to malfunction or to 【23】______ incorrect results. Minor bugs, for example a cursor that does not behave as 【24】______ can be inconvenient or frustrating, but not damaging to 【25】______ . More severe bugs can cause a program to 'hang' ( stop responding to 【26】______ and might 【27】______ the user with no 【28】______ but to restart file program. ), losing whatever 【29】______ work had not been saved. In 【30】______ case, the programmer must find and correct the error by the 【31】______ known as debugging. Because of the 【32】______ risk to important data, commercial application programs are tested and 【33】______ as completely as possible before release. Minor bugs found after the program becomes 【34】______ are corrected in next update more 【35】______ bugs can sometimes be fixed with special software, called patches, that circumvents or otherwise 【36】______ its effects. In hardware, a bug is a recurring 【37】______ problem that prevents a system or set of 【38】______ from working together properly. The 【39】______ of the term reputedly goes back to the early days of computer at Harvard University was 【40】______ a moth caught between the contacts of a relay in the machine. 【21】