In the personal computer operating systems MS-DOS and PC-DOS, a number of standard system commands were provided for common tasks such as listing files on a disk or moving files. Some commands were built-in to the command interpreter, others existed as transient commands loaded into memory when required. Over the several generations of MS DOS, commands were added for the additional functions of the operating system. In the current Microsoft Windows operating system a text-mode command prompt window can still be used. Some DOS commands carry out functions equivalent to those in a UNIX system but always with differences in details of the function.