04 tecoIntro

This document, "Introduction to TECO (Text Editor and Corrector)", from May 1972, provides a guide to the basic operations of TECO, a powerful, character-oriented text editor for the DECsystem-10. It enables users to edit any ASCII text, including programs and documents, without requiring line numbers.

Core Functionality: TECO processes text by reading "pages" (segments of text, typically separated by form feeds or limited by buffer size) into an editing buffer. Users then apply commands to modify the text in the buffer, output the edited page, and load the next. This process continues until the entire file is edited and saved. TECO supports creating new files (MAKE filename.ext) and editing existing ones (TECO filename.ext), automatically creating .BAK backup files for existing documents upon completion.

Command Structure: Commands are typically one or two letters and can be combined into "command strings" terminated by two altmode characters ($$). Numeric arguments precede commands (e.g., 3D for deleting 3 characters), while alphanumeric (text) arguments follow commands and are terminated by a single altmode (ISOMETHING$). Errors in command strings halt execution and trigger error messages. Users can correct typing mistakes using Rubout for single characters or ↑G ↑G to cancel an entire command string.

Key Command Categories:

• Input: Y (yank) clears the buffer and reads the next page. A (append) reads the next page without clearing the buffer, combining it with the existing content.
• Buffer Pointer Positioning: Editing actions occur at a movable "buffer pointer." Commands like J (move to buffer start), ZJ (move to buffer end), nC (move forward n characters), nR (move backward n characters), and nL (move n lines forward/backward) manipulate this pointer.
• Text Type-Out: T commands display text from the buffer without moving the pointer, aiding in verification (e.g., T for current line, nT for n lines, HT for the entire buffer).
• Deletion: nD deletes n characters, nK deletes n lines, and HK deletes the entire buffer.
• Insertion: I followed by the text to be inserted (terminated by altmode $ ) adds content at the pointer's position.
• Output: P outputs the buffer and reads the next page. PW outputs the buffer without clearing it or reading more text. EF closes the output file.
• Exit Commands: EX saves remaining changes and exits to the monitor. EG does the same but also re-executes the last COMPILE, LOAD, EXECUTE, or DEBUG command. ↑C ↑C aborts the TECO job, potentially losing unsaved work. A single ↑C allows a temporary exit to the monitor, preserving the buffer for re-entry.
• Search Commands: S searches for a specified string within the current buffer. N extends the search across multiple pages, automatically loading new pages as needed.

Error Handling: TECO displays error messages (?aaa) for illegal or unexecutable commands. Typing /? after an error provides more detailed information. The document advises novice users to primarily use the basic commands covered, as TECO has a much larger set of advanced functionalities detailed in the DECsystem-10 Users Handbook.