DEC-10-LCPLA-B-D Conversational Programming Language Users Manual Mar76

This document is a User's Manual for the Conversational Programming Language (CPL), designed for the DECsystem 10/20.

It serves as both a tutorial for beginners and a comprehensive reference for experienced PL/I programmers. The manual covers:

1. Foundational Elements: Basic language elements, programming statements (direct and collected), program manipulation (listing, saving, loading, executing, debugging), and an introduction to CPL's "desk calculator mode."
2. Data Management: Detailed explanations of data types (FIXED, FLOAT, CHARACTER, BIT, POINTER), variable declarations, array handling, storage classes (Automatic, Static, Controlled, Based, Parameter, Named Constant), and data conversions.
3. Control Flow and Program Structure: Assignment statements, logical expressions, conditional (IF), iterative (DO/END), and branching (GOTO, labels) statements, with an emphasis on structured and GOTO-less programming principles.
4. Modular Programming: Procedures, subroutines, functions, argument and parameter matching, recursive blocks, and block structure with scope rules.
5. Input/Output (I/O) and File Handling: Terminal I/O, formatted output (PUT EDIT), string I/O, and operations with arbitrary disk files, including file attributes, implicit/explicit OPEN/CLOSE, READ/WRITE statements.
6. Error Handling: A robust system of ON-conditions for managing various errors (e.g., ENDFILE, ERROR, ZERODIVIDE, STRINGRANGE, UNDEFINEDFILE, ATTENTION), SIGNAL to raise conditions, and REVERT.
7. Built-in Functions and Pseudo-variables: An alphabetical listing and detailed descriptions of all supported functions (e.g., SQRT, LOG, DATE, TIME, SUBSTR, ADDR, ALLOCATION).
8. System-Specific Information: Guidance on running CPL under TOPS-10 and TOPS-20 operating systems.
9. Comparison and Support: A thorough comparison of CPL with the ANSI PL/I standard, outlining CPL's subset and incompatibilities, a list of error messages with explanations and user responses, a Q&A section, and programming examples.

The manual is structured to allow readers to progressively learn CPL's features, from simple operations to advanced concepts like based storage and pointers, with clear indicators for the material's complexity.