FOCAL8-277A FOCL-F

FOCL/F (DECUS No. FOCAL8-227a), authored by D. E. Wrege from Georgia Institute of Technology in 1973, is an extended version of the 8K FOCAL/69 programming language. Developed as a user-contributed program for the DECUS Program Library (without formal quality control or warranty), it aims to enhance power and versatility for multi-disciplinary scientific, engineering, and educational applications.

Key features and extensions include:

• User-Defined Functions: Allows recursive functions with local variables and argument passing, optimizing core usage.
• Arrayed Variables: Implements more efficient variable storage (3 words per variable) and faster access.
• Machine Language Integration: Enables execution of machine language instructions (FX functions) for direct memory access, I/O device control, and bitwise operations.
• Enhanced I/O and File Handling: Introduces LIBRARY commands for device-independent input/output and a significant PS/8-OS/8 overlay for saving/loading programs and variables to disk files (PROGRAM and VARIABLE commands).
• Extended Language Features: Supports arithmetic expressions for line numbers, a line continuation character (ALTMODE), negative steps in FOR loops, a conditional subroutine call (ON command), and expanded command terminators.
• User-Defined Interrupt Service: Provides capabilities for handling custom device interrupts.
• Debugging and Utility: Offers more comprehensive error messages and a MOVE command for program text manipulation.

While largely compatible with 8K FOCAL/69, FOCL/F introduces some command variations and specific optimizations for PDP-8/E systems, such as improved TTY reader control for batch processing.