03/23/79 Incompatibilities relative to VS APL This document lists the known incompatibilities between Multics APL and IBM VS APL. The relevant manuals are "Multics APL", Order No. AK95-1, and "APL Language", GC26-3847-4. This list is subject to revision. 1. Anything that is undefined by the APL language may be different, such as the exact order of evaluation. Multics APL uses the same basic right-to-left order of evaluation as VS APL. 2. The minimum and maximum identities and the range of the )DIGITS command change as indicated in the following table: VS APL Multics APL min 7.237005577332262e75 1.70141183460492317e38 max ^7.237005577332262e75 ^1.70141183460492317e38 digits 1 - 16 1 - 19 Multics APL numbers have a larger mantissa and a smaller exponent than numbers on VS APL. 3. The comparison tolerance algorithm differs slightly between Multics APL and VS APL. Multics APL considers two numbers A and B are equal within fuzz if the following relation is true: (|A-B) <_ qCTx|A-B. Multics APL considers the value of C to be the integer fC+0.5 if (|C-fC+0.5) < qIT, where qIT is the integer tolerance. 4. The Multics APL random number operators (monadic and dyadic ?) are identical to the VS APL operators for values <^1+2*31. 5. The following VS APL commands are mapped into their Multics equivalents: )MSG send_message )MSG ON immediate_messages )MSG OFF defer_messages The following VS APL commands are unavailable in Multics APL: )OPR, )QUOTA, )STACK, and )WSSIZE. 6. The Multics login protocol is different. Multics users are denoted by a name, not a number. Multics APL is available both as a normal Multics command and as a special subsystem that confines the user to the APL environment. 7. The automatic saving of the CONTINUE workspace when a user's console is hung up is not available. 8. The error marker is placed differently in some cases. Multics APL detects some errors during function definition instead of during execution. 9. The saving of workspaces is limited by the user's Multics disk record quota, instead of by the number of workspaces. 10. Multics APL handles the ATTN key (also called LINE BREAK or QUIT) slightly differently. The ATTN key may be used for editing input and interrupting the APL interpreter. Typing mistakes may be corrected by backspacing and pressing the ATTN key; APL will type the editing prompt character: "v". As in VS APL, the LINEFEED key may also be used. The interpreter may be interrupted by pressing the ATTN key twice (or once, if no typed input is available to edit). APL will type a new-line character in response to an interrupt-type ATTN. Either overstruck O U T or an interrupt-type ATTN may be used as an escape from 'q (quad-quote) input. Multics APL usually interrupts between lines; however, long computations may be interrupted within a line. In any case, the error marker accurately shows the point of interruption. Multics APL always restarts at the beginning of a line. 11. The following errors cannot occur in Multics APL: ENTRY, q-- IMPLICIT, INTERFACE QUOTA EXHAUSTED, NO SHARES, RESEND, SYMBOL TABLE FULL, and STACK FULL. The following errors can occur in Multics APL but not in VS APL: CONTEXT, RESULT SIZE, NONCE, COMPATIBILITY, DEPTH, INTERRUPT, USAGE, FILE TIED, FILE TIE ERROR, FILE INDEX, BAD FILE, OLD FILE, FILE NAME, FILE TIE QUOTA, FILE ACCESS, BAD ACCESS MATRIX. 12. The qAV (atomic vector) system variable has been renamed to qCS (character set) to emphasize that the Multics APL character set is different from that of VS APL. 13. The qHT (horizontal tab) system variable is not available in Multics APL. By default, tabs are assumed to be set every ten spaces (the normal Multics convention). The )TABS system command may be used to change this to any other number. 14. The )SINL command is not available in Multics APL. Use )SIV. 15. The qTC (terminal control) system variable is not available in Multics APL. Use qCS. 16. Multics APL does not support the 3270 terminal. 17. VS APL implements a file system using shared variables. Multics APL does not provide shared variables, but does provide a set of system functions that implement a full APL file system, similar to the Scientific Timesharing Corp. or I. P. Sharp Associates Ltd. file systems. ----------------------------------------------------------- Historical Background This edition of the Multics software materials and documentation is provided and donated to Massachusetts Institute of Technology by Group BULL including BULL HN Information Systems Inc. as a contribution to computer science knowledge. This donation is made also to give evidence of the common contributions of Massachusetts Institute of Technology, Bell Laboratories, General Electric, Honeywell Information Systems Inc., Honeywell BULL Inc., Groupe BULL and BULL HN Information Systems Inc. to the development of this operating system. Multics development was initiated by Massachusetts Institute of Technology Project MAC (1963-1970), renamed the MIT Laboratory for Computer Science and Artificial Intelligence in the mid 1970s, under the leadership of Professor Fernando Jose Corbato. Users consider that Multics provided the best software architecture for managing computer hardware properly and for executing programs. Many subsequent operating systems incorporated Multics principles. Multics was distributed in 1975 to 2000 by Group Bull in Europe , and in the U.S. by Bull HN Information Systems Inc., as successor in interest by change in name only to Honeywell Bull Inc. and Honeywell Information Systems Inc. . ----------------------------------------------------------- Permission to use, copy, modify, and distribute these programs and their documentation for any purpose and without fee is hereby granted,provided that the below copyright notice and historical background appear in all copies and that both the copyright notice and historical background and this permission notice appear in supporting documentation, and that the names of MIT, HIS, BULL or BULL HN not be used in advertising or publicity pertaining to distribution of the programs without specific prior written permission. Copyright 1972 by Massachusetts Institute of Technology and Honeywell Information Systems Inc. Copyright 2006 by BULL HN Information Systems Inc. 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