A Note on Quad and Quote-quad

by Joseph L.F. De Kerf

Transcribed from the printed issue; not yet reviewed. Read it in the PDF of the issue, page 122

At the APL-ication Conference, M.T. Wheatley [1] presented a paper on "Extending the Domain of APL". In a footnote he states: "Formally, the names of system functions and variables may begin with either ⎕ or ⍞, however, to date no ⍞ names, other than ⍞ itself, have been introduced."

This is true, as far as IBM implementations of APL are concerned, but distinguished names beginning with the Quote-Quad ⍞ have really been implemented, namely in 4000 APL (General Electric Computers GEC) [2] and in WATCOM APL (WATCOM Products) [3].

4000 APL supports two modes of file handling: component files, which are intended only for access by APL, and logical files, which enable the user to access files created or processed by other languages. Distinguished names related to the use of component files begin with the Quad ⎕, while distinguished names related to logical files begin with the Quote-Quad ⍞. The following logical file system functions are available:


`⍞CNTRL`	Executes a data management control command
`⍞CONN`	Connects a file and associates a tie number
`⍞CREATE`	Creates a file or catalogue
`⍞DCONN`	Connects a device and associates a tie number
`⍞READ`	Reads a record from the specified file
`⍞REPL`	Replaces a record in the specified file
`⍞SEEK`	Seeks for a record or key in the specified file
`⍞WRITE`	Outputs a record to the specified file

WATCOM APL too supports component and native files. Distinguished names related to both modes of file handling begin with the Quad ⎕, except the names of the system functions to perform character stream input and output for native files operations, which begin with the Quote-Quad ⍞:


`⍞GET`	Get character string from the specified file
`⍞PUT`	Put character string to the specified file

It should be noticed that in some implementations of APL such as APL*PLUS/PC et al (STSC) [4], the distinction between the distinguished names related to component and native files is detectable by the fact that the second character in the name is the letter F or N respectively, e.g. ⎕FREAD and ⎕FWRITE for component files versus ⎕NREAD and ⎕NWRITE for native files. This may be less remarkable, but it avoids the use of an overstruck character.

References¶

[1] M.T. Wheatley: Extending the Domain of APL; APL-ication Conference Proceedings, University of Kent, England, 28-30 September 1988; British APL Association BAA, London, England, 1988, pp.1-7.

[2] APL For OS4000 User Software Handbook: Publ. No. DD 1558; GEC Computers Limited, Borehamwood, Hertfordshire, England, October 1980.

[3] J.C. Wilson and T.A. Wilkinson: WATCOM APL Users’ Guide (IBM PC with DOS); WATCOM Publications Limited, Waterloo, Ontario, Canada, May 1983.

[4] APL*PLUS System for the PC - Reference Manual: STSC Incorporated, Technical Documentation, Rockville, Maryland, 1986.