Editing Peripheral Interchange Program (section)

==PIP in CP/M and MP/M==
[[File:CPM-86.png|thumb|<code>PIP.CMD</code> in [[CP/M-86]]]]
[[File:Digital Research DOS Plus Version 1.2 720x400.png|thumb|Example using the <code>PIP</code> command in [[DOS Plus]] to create a text file from {{tt|CON:}} console input]]
[[Gary Kildall]], who developed [[CP/M]] and [[MP/M]], based much of the design of its file structure and command processor on operating systems from Digital Equipment, such as [[RSTS/E]] for the PDP-11. Besides accessing files on a [[floppy disk]], the PIP command in CP/M could also transfer data to and from the following "special files":
*{{tt|CON:}} — [[System console|console]] (input and output)
*{{tt|AUX:}} — an auxiliary device. In CP/M 1 and 2, PIP used {{tt|PUN:}} (paper tape punch) and {{tt|RDR:}} (paper tape reader) instead of {{tt|AUX:}}
*{{tt|LST:}} — list output device, usually the [[computer printer|printer]]
*{{tt|PRN:}} — as {{tt|LST:}}, but lines were numbered, tabs expanded and form feeds added every 60 lines
*{{tt|[[Null device|NUL:]]}} — null device, akin to [[Null device|\Device\Null]] and [[Null device|/dev/null]]
*{{tt|EOF:}} — input device that produced [[end-of-file]] characters, [[ASCII]] {{tt|0x1A}}
*{{tt|INP:}} — custom input device, by default the same as {{tt|EOF:}}
*{{tt|PUN:}} — punch card unit:
*{{tt|OUT:}} — custom output device, by default the same as {{tt|NUL:}}

These were not true [[device file]]s, however, because their handling was limited to PIP. The two custom devices {{tt|INP:}} and {{tt|OUT:}} were implemented as calls to fixed locations at the start of the PIP program; the intention was that the user, or the [[Original Equipment Manufacturer|OEM]], could [[Software patch|patch]] these locations to add their own input or output devices. 246 bytes of free space were left in the program for this purpose.

In addition to the usual <code>PIP destination=source</code> syntax, PIP under CP/M still allowed the old <code>PIP destination_source</code> form. This behaviour was not documented, and CP/M generally did not have a standard for which characters could appear in file names; therefore other programs could and did create filenames containing underscore characters, which PIP could not handle.