Focal

Summary

This document is an introductory guide and manual for FOCAL, a conversational programming language developed by the Digital Equipment Corporation (DEC) for their PDP-8 family of small computers.

The document is structured into two main parts:

• Part 1: Introduces the basic concepts of computing, emphasizing that computers are fast, accurate, and perfectionist machines that require human instructions to operate. It uses simple, practical examples—specifically, a program to calculate simple interest—to demonstrate how to write, store, and execute programs using FOCAL. It also covers how the language can be used for more complex, iterative, or "personal" tasks.
• Part 2: Demonstrates FOCAL's capabilities for more advanced mathematical tasks, such as generating tables of squares and square roots, solving for the intersection of functions, plotting graphs on a terminal, and performing series evaluations.

The document concludes with technical appendices, including a comprehensive list of FOCAL functions, a summary of error diagnostics, and a quick-reference guide to FOCAL commands and mathematical operators, serving as a reference for users to begin programming.