FORTRAN Language Manual Feb87

This document is the TOPS-10/TOPS-20 FORTRAN Language Manual (AA-N383B-TK), published in May 1985 by Digital Equipment Corporation. It describes the language elements for FORTRAN-10 and FORTRAN-20, which are compatible with the FORTRAN-77 standard and include various extensions (highlighted in blue print within the manual). It supersedes a previous version (AA-N383A-TK) and is intended for use with TOPS-10 V7.02 and TOPS-20 V4.1/V5.1 operating systems, and FORTRAN-10/20 V10 software.

The manual is organized into three main parts:

1. Language Elements (Chapters 2-5): Covers the fundamental components of FORTRAN programs, including:

   • Character set and line structure (initial, continuation, comment, debug, blank, line-sequenced).
   • Various data types for constants (integer, real, double-precision, complex, character, octal, double-octal, logical, Hollerith, statement label).
   • Symbolic names, variables, and arrays (subscripts, dimensioning, storage order, character substrings).
   • Expressions (arithmetic, logical, relational) and their evaluation rules.

2. Statements (Chapters 6-14): Details the different types of FORTRAN statements:

   • Distinguishes between executable and nonexecutable statements.
   • Describes compilation control statements (PROGRAM, INCLUDE, END).
   • Explains specification and data statements (DIMENSION, TYPE, IMPLICIT, COMMON, EQUIVALENCE, EXTERNAL, INTRINSIC, PARAMETER, DATA, SAVE).
   • Covers assignment statements (arithmetic, logical, statement label, character).
   • Outlines control statements (GO TO, IF, DO, DO WHILE, CONTINUE, STOP, PAUSE, END DO).
   • Details data transfer statements (READ, WRITE, REREAD, ACCEPT, TYPE, PRINT, PUNCH, ENCODE/DECODE, internal files).
   • Describes file-control (OPEN, CLOSE) and device-control statements.
   • Explains formatted data transfers, including FORMAT statements, edit descriptors, and I/O list interaction.
   • Discusses functions and subroutines (intrinsic, statement, external, and FORTRAN-supplied/user-defined subroutines) and block data subprograms.

3. Language Usage (Chapters 15-19): Provides guidance on writing and managing FORTRAN programs:

   • General programming considerations, including accuracy, portability, and optimization techniques.
   • Instructions for using the FORTRAN-10 and FORTRAN-20 compilers, their switches, and interpreting compiler listings and error reports.
   • Details on the FORTRAN Interactive Debugger (FORDDT) for testing and debugging.
   • Information on the FORTRAN Object Time System (FOROTS), its features, I/O facilities, and memory management.
   • Guidance on using FORTRAN real-time software (TOPS-10 only), including subroutines like LOCK, RTINIT, and RTSTRT.

The manual also includes several appendices summarizing FORTRAN statements, the ASCII character code set, compiler error messages, FOROTS error messages, FORDDT error messages, and FORTRAN-supplied plotter subroutines.