VAX-11 Fortran IV-Plus Language Reference Manual

This document, the VAX-11 FORTRAN IV-PLUS Language Reference Manual, published in August 1978 by Digital Equipment Corporation, serves as a comprehensive reference guide for the FORTRAN language elements supported by the VAX-11 FORTRAN IV-PLUS system. It is specifically designed to assist programmers in preparing FORTRAN source programs, and explicitly states it is not a tutorial nor does it cover the FORTRAN user interface to the VAX/VMS operating system.

The manual details the language by:

• Introducing VAX-11 FORTRAN IV-PLUS: Highlighting its foundation in ANS FORTRAN X3.9-1966 along with significant enhancements such as the CHARACTER data type, Block IF statements, arithmetic expressions as array subscripts, mixed-mode expressions, new data types (e.g., LOGICAL*1, INTEGER*2), the IMPLICIT statement, various new I/O statements (ACCEPT, TYPE, PRINT, ENCODE/DECODE, OPEN, CLOSE, DEFINE FILE, FIND), PARAMETER statements, generic functions, and extended DO loop capabilities. It also covers program unit structure, line formatting (including inline comments and debugging statements), and the INCLUDE statement.
• Describing FORTRAN Statement Components: Explaining symbolic names, various data types (Integer, Real, Double Precision, Complex, Logical, Character) and their storage requirements, different types of constants (including Octal and Hexadecimal), variables, arrays (declarators, subscripts, storage, adjustable arrays), character substrings, and the structure and evaluation of expressions (Arithmetic, Character, Relational, Logical).
• Detailing Assignment Statements: Covering Arithmetic, Logical, Character, and ASSIGN statements.
• Explaining Control Statements: Outlining GO TO (Unconditional, Computed, Assigned), IF statements (Arithmetic, Logical, Block IF constructs), DO loops (including nesting and extended range), CONTINUE, CALL, RETURN, PAUSE, STOP, and END statements.
• Presenting Specification Statements: Describing non-executable statements like IMPLICIT, TYPE DECLARATION, DIMENSION, COMMON, EQUIVALENCE (including array and substring equivalences and interaction with COMMON), EXTERNAL, DATA, PARAMETER, PROGRAM, and BLOCK DATA.
• Covering Subprograms: Discussing subprogram arguments, built-in functions (%VAL, %REF, %DESCR, %LOC), user-written subprograms (Arithmetic Statement Functions, Function, Subroutine, ENTRY statements), and FORTRAN library functions (Processor-Defined, Generic, Character functions).
• Outlining Input/Output (I/O) Statements: Detailing components such as logical unit numbers, direct access record numbers, format specifiers, and I/O lists. It then explains Formatted Sequential, List-Directed Sequential, Unformatted Sequential, Formatted Direct Access, Unformatted Direct Access I/O, as well as ENCODE and DECODE statements, and error handling (END=s, ERR=s).
• Dedicated to FORMAT Statements: Providing an in-depth look at various field descriptors (e.g., I, O, Z, F, E, D, G, L, A, H, X, T, Q, $, :), carriage control, format specification separators, external field separators, run-time formats, and rules for writing FORMAT statements.
• Describing Auxiliary I/O Statements: Explaining file management functions like OPEN, CLOSE, REWIND, BACKSPACE, FIND, ENDFILE, and DEFINE FILE, along with their associated keywords and parameters.

The document also includes appendices summarizing FORTRAN and ASCII character sets, Radix-50 constants, expression operators, and a detailed list of FORTRAN library functions.