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ParadigmsMulti-paradigm: concurrent, imperative
Designed byCharles H. Lindsey
First appeared1977; 45 years ago (1977)
Typing disciplinestatic, strong, safe, structural
Implementation languageBLISS
PlatformMotorola 680x0, Sun SPARC
OSSunOS, Solaris, GEMDOS

ALGOL 68S is a programming language designed as a subset of ALGOL 68, to allow compiling via a one-pass compiler.[1] It was mostly for numerical analysis.


A compiler for ALGOL 68S was available for the PDP-11, written in the language BLISS. The multiprocessor version designed for the C.mmp[2] has been preserved at the PDP Unix Preservation Society archive.[3]

Charles H. Lindsey created another implementation of ALGOL 68, named ALGOL 68S, for Sun-3, Sun SPARC (under SunOS 4.1), Sun SPARC (under Solaris 2), Atari ST (under GEMDOS) and Acorn Archimedes (under RISC OS), c.f. Charles Lindsey's Home Page

Chief differences from ALGOL 68[edit]

The main differences between ALGOL 68 and 68S, as summarised from Appendix 4 of the Informal Introduction,[4] include:

  • No union
  • No flex, but strings are handled specially
  • No arrays inside structures (but references to arrays were allowed) and a similar restriction on arrays of arrays (multidimensional arrays are nonetheless permitted)
  • Limits on use of long and short to aid implementing on small computers
  • No heap
  • No parallel processing
  • Limits on the order of declaration and other small syntactic differences to allow one-pass compiling
  • No formats


  1. ^ Hibbard, P.G. (May 1977). "A Sublanguage of ALGOL 68". SIGPLAN Notices. 12 (5): 71–79. doi:10.1145/954652.1781177. S2CID 37914993.
  2. ^ {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)[permanent dead link] Description of C.mmp A68S implementation.
  3. ^ "Archived copy". Archived from the original on 20 July 2008. Retrieved 13 January 2022.{{cite web}}: CS1 maint: archived copy as title (link)
  4. ^ Lindsey, C. H.; van der Meulen, S. G. (1977). Informal Introduction to Algol 68. North-Holland.