Subsequent work was done on the compiler after Bourne left Cambridge University in 1975. Garbage collection was added, and the code base is still running[clarification needed] on an emulated OS/MVT using Hercules.
The ALGOL 68C compiler generated output in ZCODE, a register-based intermediate language, which could then be either interpreted or compiled to a native executable. This ability to interpret or compile ZCODE encouraged the porting of ALGOL 68C to many different computing platforms. Aside from the CAP computer, the compiler was ported to systems including Conversational Monitor System (CMS), TOPS-10, and Zilog Z80.
A very early predecessor of this compiler was used by Guy and Bourne to write the first Game of Life programs on the PDP-7 with a DEC 340 display.[2][3]
Stephen Bourne subsequently reused ALGOL 68's if ~ then ~ else ~ fi, case ~ in ~ out ~ esac and for ~ while ~ do ~ od clauses in the common UnixBourne shell, but with in's syntax changed, out removed, and od replaced with done (to avoid conflict with the od utility).
After Cambridge, Bourne spent nine years at Bell Labs with the Version 7 Unix (Seventh Edition Unix) team. As well as developing the Bourne shell, he ported ALGOL 68C to Unix on the DEC PDP-11-45 and included a special option in his Unix debuggerAdvanced Debugger (adb) to obtain a stack backtrace for programs written in ALGOL 68C. Here is an extract from the Unix 7th edition manual pages:[4]
NAME adb - debugger SYNOPSIS adb [-w] [ objfil [ corfil ] ] [...] COMMANDS [...] $modifier Miscellaneous commands. The available modifiers are: [...] a ALGOL 68 stack backtrace. If address is given then it is taken to be the address of the current frame (instead of r4). If count is given then only the first count frames are printed.
ALGOL 68C extensions to ALGOL 68
Below is a sampling of some notable extensions:[5]
Automatic op:= for any operator, e.g. *:= and +:=
UPTO, DOWNTO and UNTIL in loop-clauses;
displacement operator (:=:=)
ANDF, ORF and THEFsyntactic elements.
separate compilation - ENVIRON clause and USING clause
scopes not checked
bounds in formal-declarers
CODE ... EDOC clause - for embedding ZCODE
The ENVIRON and USING clauses
Separate compilation in ALGOL 68C is done using the ENVIRON and USING clauses. The ENVIRON saves the complete environment at the point it appears. A separate module written starting with a USING clause is effectively inserted into the first module at the point the ENVIRON clause appears.
ENVIRON and USING are useful for a top-down style of programming, in contrast to the bottom-up style implied by traditional library mechanisms.
These clauses are kind of the inverse of the #include found in the C programming language, or import found in Python. The purpose of the ENVIRON mechanism is to allow a program source to be broken into manageable sized pieces. It is only necessary to parse the shared source file once, unlike a #include found in the C programming language where the include file needs to be parsed for each source file that includes it.
Example of ENVIRON clause
A file called mylib.a68:
BEGIN INT dim = 3; # a constant # INT a number := 120; # a variable # ENVIRON EXAMPLE1; MODE MATRIX = [dim, dim]REAL; # a type definition # MATRIX m1; a number := ENVIRON EXAMPLE2; print((a number)) END
Example of USING clause
A file called usemylib.a68:
USING EXAMPLE2 FROM "mylib" BEGIN MATRIX m2; # example only # print((a number)); # declared in mylib.a68 # print((2 UPB m1)); # also declared in mylib.a68 # ENVIRON EXAMPLE3; # ENVIRONs can be nested # 666 END
Restrictions to the language from the standard ALGOL 68
No ALGOL 68 FLEX and variable length arrays
MODE STRING implemented without FLEX
The PAR parallel clause was not implemented
Nonstandard transput
others...
A translator–compiler for ALGOL 68C was available for the PDP-10, IBM System/360 and several other computers.
References
^Birrell, Andrew D. (December 1977). "System Programming in a High Level Language" (PDF). Dissertation submitted for the degree of Doctor of Philosophy. University of Cambridge. Retrieved 2007-04-22.
^"Item Detail: Digital Equipment Corporation Model 340". Australian Computer Museum Society (ACMS). AceWare Web Hosting. Retrieved 2020-04-17.
^Gardner, Martin (October 1970). "The fantastic combinations of John Conway's new solitaire game "life"" (PDF). Mathematical Games. Scientific American. No. 223. pp. 120–123. For long-lived populations such as this one Conway sometimes uses a PDP-7 computer with a screen on which he can observe the changes [...] The program was written by M. J. T. Guy and S. R. Bourne. Without its help some discoveries about the game would have been difficult to make.
^. UnixDev.net. Archived from the original on 2016-03-03. Retrieved 2020-04-17.
^Bourne, Stephen R.; Birrell, Andrew D.; Walker, Ian (1975). ALGOL 68C reference manual. Cambridge University Computer Laboratory.
External links
Official website
– includes 10+ publication references.
A Transportation of ALGOL 68C – PJ Gardner, University of Essex – March 1977 (From 370 to DECsystem-10)
Running ALGOL 68C on MVS - how to install ALGOL 68C on an emulated MVS system
February 18, 2023
algol, this, article, need, reorganization, comply, with, wikipedia, layout, guidelines, please, help, editing, article, make, improvements, overall, structure, july, 2016, learn, when, remove, this, template, message, this, article, needs, additional, citatio. This article may be in need of reorganization to comply with Wikipedia s layout guidelines Please help by editing the article to make improvements to the overall structure July 2016 Learn how and when to remove this template message This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources ALGOL 68C news newspapers books scholar JSTOR August 2012 Learn how and when to remove this template message ALGOL 68C is an imperative computer programming language a dialect of ALGOL 68 that was developed by Stephen R Bourne and Michael Guy to program the Cambridge Algebra System CAMAL The initial compiler was written in the Princeton Syntax Compiler PSYCO by Edgar T Irons that was implemented by J H Mathewman at Cambridge ALGOL 68 CambridgeDeveloper s Stephen Bourne Michael Guy Andrew D Birrell Ian Walker Chris Cheney et al Initial releasecirca 1970 53 years ago 1970 Stable release1 3039 March 3 2013 9 years ago 2013 03 03 Written inALGOL 68Operating systemIBM 360 370 etc mainframes or emulations running MVT or MVSTypeCompiler translatorWebsitebitbucket wbr org wbr algol68c wbr dlALGOL 68C was later used for the CHAOS OS for the capability based security CAP computer at University of Cambridge in 1971 Other early contributors were Andrew D Birrell 1 and Ian Walker Subsequent work was done on the compiler after Bourne left Cambridge University in 1975 Garbage collection was added and the code base is still running clarification needed on an emulated OS MVT using Hercules The ALGOL 68C compiler generated output in ZCODE a register based intermediate language which could then be either interpreted or compiled to a native executable This ability to interpret or compile ZCODE encouraged the porting of ALGOL 68C to many different computing platforms Aside from the CAP computer the compiler was ported to systems including Conversational Monitor System CMS TOPS 10 and Zilog Z80 Contents 1 Popular culture 2 Algol 68C and Unix 3 ALGOL 68C extensions to ALGOL 68 3 1 The ENVIRON and USING clauses 3 1 1 Example of ENVIRON clause 3 1 2 Example of USING clause 4 Restrictions to the language from the standard ALGOL 68 5 References 6 External linksPopular culture EditA very early predecessor of this compiler was used by Guy and Bourne to write the first Game of Life programs on the PDP 7 with a DEC 340 display 2 3 Various Liverpool Software Gazette issues detail the Z80 implementation The compiler required about 120 KB of memory to run hence the Z80 s 64 KB memory is actually too small to run the compiler So ALGOL 68C programs for the Z80 had to be cross compiled from the larger CAP computer or an IBM System 370 mainframe computer Algol 68C and Unix EditStephen Bourne subsequently reused ALGOL 68 s u b if b u u then u u else u u b fi b u u b case b u u in u u out u u b esac b u and u for u u while u u b do b u u b od b u clauses in the common Unix Bourne shell but with u in u s syntax changed u out u removed and u od u replaced with u done u to avoid conflict with the od utility After Cambridge Bourne spent nine years at Bell Labs with the Version 7 Unix Seventh Edition Unix team As well as developing the Bourne shell he ported ALGOL 68C to Unix on the DEC PDP 11 45 and included a special option in his Unix debugger Advanced Debugger adb to obtain a stack backtrace for programs written in ALGOL 68C Here is an extract from the Unix 7th edition manual pages 4 NAME adb debugger SYNOPSIS adb w objfil corfil COMMANDS modifier Miscellaneous commands The available modifiers are a ALGOL 68 stack backtrace If address is given then it is taken to be the address of the current frame instead of r4 If count is given then only the first count frames are printed ALGOL 68C extensions to ALGOL 68 EditBelow is a sampling of some notable extensions 5 Automatic op for any operator e g and UPTO DOWNTO and UNTIL in loop clauses displacement operator ANDF ORF and THEF syntactic elements separate compilation ENVIRON clause and USING clause scopes not checked bounds in formal declarers CODE EDOC clause for embedding ZCODEThe ENVIRON and USING clauses Edit Separate compilation in ALGOL 68C is done using the ENVIRON and USING clauses The ENVIRON saves the complete environment at the point it appears A separate module written starting with a USING clause is effectively inserted into the first module at the point the ENVIRON clause appears ENVIRON and USING are useful for a top down style of programming in contrast to the bottom up style implied by traditional library mechanisms These clauses are kind of the inverse of the include found in the C programming language or import found in Python The purpose of the ENVIRON mechanism is to allow a program source to be broken into manageable sized pieces It is only necessary to parse the shared source file once unlike a include found in the C programming language where the include file needs to be parsed for each source file that includes it Example of ENVIRON clause Edit A file called mylib a68 BEGIN INT dim 3 a constant INT a number 120 a variable ENVIRON EXAMPLE1 MODE MATRIX dim dim REAL a type definition MATRIX m1 a number ENVIRON EXAMPLE2 print a number END Example of USING clause Edit A file called usemylib a68 USING EXAMPLE2 FROM mylib BEGIN MATRIX m2 example only print a number declared in mylib a68 print 2 UPB m1 also declared in mylib a68 ENVIRON EXAMPLE3 ENVIRONs can be nested 666 ENDRestrictions to the language from the standard ALGOL 68 EditNo ALGOL 68 FLEX and variable length arrays MODE STRING implemented without FLEX The PAR parallel clause was not implemented Nonstandard transput others A translator compiler for ALGOL 68C was available for the PDP 10 IBM System 360 and several other computers References Edit Birrell Andrew D December 1977 System Programming in a High Level Language PDF Dissertation submitted for the degree of Doctor of Philosophy University of Cambridge Retrieved 2007 04 22 Item Detail Digital Equipment Corporation Model 340 Australian Computer Museum Society ACMS AceWare Web Hosting Retrieved 2020 04 17 Gardner Martin October 1970 The fantastic combinations of John Conway s new solitaire game life PDF Mathematical Games Scientific American No 223 pp 120 123 For long lived populations such as this one Conway sometimes uses a PDP 7 computer with a screen on which he can observe the changes The program was written by M J T Guy and S R Bourne Without its help some discoveries about the game would have been difficult to make The Modular Manual Browser Adb UnixDev net Archived from the original on 2016 03 03 Retrieved 2020 04 17 Bourne Stephen R Birrell Andrew D Walker Ian 1975 ALGOL 68C reference manual Cambridge University Computer Laboratory External links EditOfficial website Cambridge ALGOL 68 on the historical roster of computer languages includes 10 publication references A Transportation of ALGOL 68C PJ Gardner University of Essex March 1977 From 370 to DECsystem 10 Running ALGOL 68C on MVS how to install ALGOL 68C on an emulated MVS system Retrieved from https en wikipedia org w index php title ALGOL 68C amp oldid 1035987966, wikipedia, wiki, book, books, library,
