PDP-6 FORTRAN II Language

This document serves as a reference manual for PDP-6 FORTRAN II, assuming the reader has a basic understanding of FORTRAN programming. It comprehensively outlines the language's specific statements and capabilities.

The manual begins by detailing the fundamental elements of FORTRAN II, including its character set, various FORTRAN words (constants, variables, operators, labels, commands), and number representations (integer, real, Boolean, and ASCII constants). It explains variable naming conventions, subscripted variables, and general program formation rules for both card and paper tape input.

Subsequent chapters delve into different statement types:

• Assignment Statements cover arithmetic and Boolean expressions, their operators, formation rules, and evaluation procedures, including the use of parentheses.
• Specification Statements (DIMENSION, COMMON, EQUIVALENCE) are explained for declaring arrays, sharing storage locations between program units, and assigning multiple variables to the same memory address, respectively.
• Control Statements (GO TO, IF, DO, CONTINUE, PAUSE, STOP) dictate the program's execution flow, including conditional and unconditional branching, loop control, and program termination. Special IF statements for sense lights, switches, and overflow conditions are also covered.
• Subprograms distinguish between user-defined External Functions and Subroutines, and predefined Intrinsic Functions, outlining their definition, calling conventions, and argument handling.
• Input-Output (I/O) operations describe I/O lists, executable statements (READ, WRITE, tape commands), and FORMAT statements, which specify data arrangement, conversion using various field descriptors (F, E, G, I, O, L, A, H, X), scale factors, repeat counts, and carriage control for printed output.

The document also includes several appendices covering compiler and assembler diagnostics, special PDP-6 FORTRAN II features like DECtape I/O and the TITLE statement, integration with MACRO-6 assembly code, FORTRAN II operating system details (device assignments, library programs like EXIT, PDUMP, DUMP, CHANG), compiler operating instructions, and specific limitations of the 9K FORTRAN II compiler (e.g., no Boolean statements or '*' in IF statements).