COMP.COM (among other commands) in IBM PC DOS 1.0.
In DOS, the comp command first appeared in PC DOS 1.0[7] and has been included in most versions of MS-DOS and PC DOS. A newer command, fc was added in DOS 3.3 which allows for line comparisons in addition to binary comparisons. DR DOS 6.0 also includes an implementation of the comp command.[8]
The FreeDOS version was developed by Paul Vojta and is licensed under the MIT License.[9] Ged Murphy developed the ReactOS version. It is licensed under the GNU GPL 2.[10]