Focl/S, an Expanded Language for Small Computers, Based on FOCAL

Summary FOCL/S is an expanded, single-user version of the FOCAL/69 programming language designed for 8K PDP-8/12 computers. It is intended to be a superset of FOCAL/69, maintaining syntactic compatibility while introducing several enhancements, including:

• Memory Management: Text, variables, and the pushdown list have been moved to Field 1, which provides more efficient core usage and enables user-defined functions in Field 0.
• Data Structures: Support for up to 8 multiple-subscripted arrays (up to 4 dimensions each) in a common storage area.
• Expanded Functionality: Introduction of the FX(N, ...) function for direct core memory access, machine language instruction execution, logical "AND" operations between expressions, and octal-decimal conversions.
• Programming Features: Includes an "ON" command (a three-branch conditional "DO"), support for arithmetic expressions in line number calculations, and a continuation character (Control/K) for longer command lines.
• Debugging and Compatibility: Designed for XOD compatibility for easier debugging and includes modified error diagnostic reporting.

The document also provides comprehensive technical details regarding core maps for Field 0 and Field 1, a list of extended/modified system routines, and a full table of error diagnostic codes.