Sequence Break DECAL(ID:7956/)

BBN version of DEC simplified Algol 

DECAL-BBN with sequence break capabilities and a formatting ouput language (similar to picture?)
Related languages
DECAL-BBN => Sequence Break DECAL   Enhancement of
References:
  • McQuillin, Richard J. "Some New Developments in the DECAL Compiler" view details Abstract: This paper describes work being carried on by the author for the Decision Sciences Laboratory, ESD, as well as other work that has recently been completed on the development of DECAL.
    The basic 1-core version of DECAL was released in its present form as DECAL-BBN in September, 1963. Since that time there has been a general increase in memory capacity of many PDP-l's, and DECAL has likewise been expanding. The first development was the moving of the compiler's symbol table into the second core field. This al lowed large programs with many symbols to be compiled. Next came a 2-core modification to allow the compilation to be carried out in sequence break mode. This doubled the speed of compilation. Recently there has been a further modification to compile programs written in ASCII source language .
    The author has been carrying on work to extend the DECAL language. In particular the work has been in the area of allowing real (floating-point) variables and constants to be handled automatically in algebraic statements. The other area of work has been to implement input/output facilities in the DECAL language. This has lead to the development of a language similar to the FORTRAN input, output, and format statements.
    Finally the author will discuss the desirability of implementation of DECAL on the other PDP computers. DECAL has been developed into a powerful and elegant language through many man-years of effort. Perhaps consideration should be given to other machines, specifically the PDP-6 and PDP-7.
    Extract: Introduction
    Introduction
    DECAL, Digital Equipment Corporation Algorithmic Language, in its original form, came into being in 1960 as the first algebraic compiler for a DEC computer. It was designed with some very advanced features still applicable to today's compilers, and has been well proven as a compiler for the professional programmer. In fact, as an assembler-compiler, DECAL can be used when a mixture of both machine codes and problem-oriented language is required. The problem-oriented language is similar to ALGOL in call-by-value procedures and conditional statements, and in statements and subscripted variable handling . Dynamic array handling is also allowed. The compiler does not process recursive procedures, call-by-name procedures, or its own variables.
    The object code produced by DECAL is an intermediate code which is then loaded into core in binary by the DECAL Linking Loader. All source programs are compiled relative to a common origin. At load time they are processed in any order by the DLL and automatically relocated with symbols cross-linked between the various programs. The DLL can accept a library tape on which all utility subroutines may be stored.
    The present generation of DECAL compilers was initiated in 1962, by the author and his associates at Bolt, Beranek and Newman, Inc . , and is known as DECAL-BBN. This is a one-core version which contains all the features of the language described in the DECAL-BBN Programming Manual which is used today. It was soon decided, however, that one core did not allow enough room for future system expansion or for compilations of large programs, and was too restrictive because most users had more than one core memory on their computers.
    It was decided to move the symbol table to the second core, and this new version became known as 2-core DECAL-BBN. A subsequent version, Sequence Break DECAL, provided for the reader, punch, and typewriter to operate under program interrupt control, making compilation about twice as fast.
    The next major development came from BBN under sponsorship of the Decision Sciences Laboratory. The DSL PDP-1 Complex had grown to include ASR-33Teletypes and a Type 164 Line Printer, both of which used ASCII code. DECAL and DECAL Loader were modified to accept ASCII code as source codes as well as to compile strings into ASCII code. The nonalphabetic codes, mostly for the instruction generators, were modified to be compatible with the ASCII character set. For example, the FIODEC codes representing instruction generators such as "A " and "V" were changed to "AND " and "OR"; the symbol "AND" was made to have meaning both in an algebraic statement (A AND B => C) or in an instruction statement (AND B). This Teletype DECAL will be embedded into a DSL Monitor System able to compile, load, and go through a sophisticated monitor built around the Type 24 Serial Drum.
          in DECUS Spring Conference 1965 view details