Introduction to U/W-Focal for the PDP/8

Summary

This document serves as a user manual for U/W-FOCAL (UWF), an interactive, stack-processing programming language designed for the Digital Equipment Corporation PDP/8 computer. UWF is described as an advanced, easier-to-use version of FOCAL, borrowing concepts from BASIC and FORTRAN.

The manual covers the following key areas:

• System Requirements and Setup: Minimum 8K memory configuration, binary tape loading procedures, and switch register settings for custom configurations.
• Operational Fundamentals: Explanations of command modes (direct vs. indirect), line numbering, punctuation, and the use of the symbol table.
• Editing and I/O: Procedures for using editing commands (WRITE, ERASE, MODIFY, MOVE) and I/O commands (ASK, TYPE) including special operators for formatting, tabbing, and device selection (terminal, high-speed reader, and punch).
• Arithmetic and Logic: Detailed guide on arithmetic operators, operator priority, and branch/control commands (GOTO, DO, IF, ON, JUMP, LINK, QUIT, RETURN).
• Loop Management: Use of FOR, NEXT, and BREAK commands for horizontal and vertical loop structures.
• Functions: Extensive documentation on built-in internal functions (mathematical, trigonometric, and character processing), as well as the implementation of custom Program Defined Functions (PDFs).
• Advanced Features: Use of protected ("secret") variables, machine-level access via the FPAL function, and error message diagnostics.
• Appendix: Includes a list of machine-code patches for custom features and a comprehensive table of character codes.