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Peripheral Interchange Program (PIP) was a utility to transfer files on and between devices onDigital Equipment Corporation's computers. It was first implemented on thePDP-6 architecture by Harrison "Dit" Morse early in the 1960s. It was subsequently implemented for DEC's operating systems forPDP-10,PDP-11, andPDP-8^[1] architectures.In the 1970s and 1980sDigital Research implemented PIP onCP/M^[2] andMP/M.^[3]

It is said that during development it was named ATLATL, which is an acronym for "Anything, Lord, to Anything, Lord."^[4] This humorously described both its purpose as a device-independentfile copying tool and the difficulties at the time of safely copying files between devices.

The original PIP syntax was

PIP destination←source /switches

using the left-arrow character from theASCII-1963 character set that theFlexowriter keyboards of the time used. As other terminals were introduced that used later versions of ASCII (without the left-arrow character), PIP allowed the syntax

PIP destination=source

Theunderscore (_) character, which was in the same ASCII character position that left-arrow had occupied, was still supported to separate the destination and source specifications.

Source and destination werefile specification strings. These consisted of a device name, typically 2 characters for device type such as DK (disk), LP (line printer), MT (magnetic tape), etc. and a unit number from 0 to 7, a colon (:), filename and extension.

Copying was generally permitted between any file specification to any other where it made sense.

Early versions ofVAX/VMS implemented certainDCL commands, such asDIRECTORY andRENAME, by runningRSX-11M PIP in compatibility mode. This usage of PIP was replaced by VAX-specific code in VAX/VMS 2.0,^[5] but PIP remained as part of the VAX-11 RSX layered product for VMS.^[6]

As late as the mid-1980s, PIP was still in common use onTOPS-10,TOPS-20 andPDP-11 systems.

Gary Kildall, who developedCP/M andMP/M, based much of the design of its file structure and command processor on operating systems from Digital Equipment, such asRSTS/E for the PDP-11. Besides accessing files on afloppy disk, the PIP command in CP/M could also transfer data to and from the following "special files":

• CON: —console (input and output)
• AUX: — an auxiliary device. In CP/M 1 and 2, PIP usedPUN: (paper tape punch) andRDR: (paper tape reader) instead ofAUX:
• LST: — list output device, usually theprinter
• PRN: — asLST:, but lines were numbered, tabs expanded and form feeds added every 60 lines
• NUL: — null device, akin to\Device\Null and/dev/null
• EOF: — input device that producedend-of-file characters,ASCII0x1A
• INP: — custom input device, by default the same asEOF:
• PUN: — punch card unit:
• OUT: — custom output device, by default the same asNUL:

These were not truedevice files, however, because their handling was limited to PIP. The two custom devicesINP: andOUT: were implemented as calls to fixed locations at the start of the PIP program; the intention was that the user, or theOEM, couldpatch 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 usualPIP destination=source syntax, PIP under CP/M still allowed the oldPIP destination_source 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.

The PIP program is the reason forreserved filenames in Microsoft Windows:CONPRNAUXNULCOM0COM1COM2COM3COM4COM5COM6COM7COM8COM9LPT0LPT1LPT2LPT3LPT4LPT5LPT6LPT7LPT8LPT9. This limitation is case-insensitive, and also applies to basenames. So for example,Con.txt is an invalid filename.

• copy (command) – RT-11, RSX-11, OpenVMS, AmigaOS, DOS, OS/2 and Microsoft Windows command for copying data
• cp (Unix) – Unix command for copying data
• Kermit (protocol)

• CP/M software
• File copy utilities

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