M-1101 Sep61

This document describes the Typewriter Control (TYC) program (M-1101), a utility designed to aid in debugging and controlling other computer programs directly from an on-line typewriter, specifically for the PDP-1. TYC is programmed in DECAL and FRAP, and operates by entering a waiting loop for user input.

Key functionalities of TYC include:

• Setting and Examining Memory: Users can set the program counter (PC) to a specific address (a), display the contents of the current address (w), or increment the PC and display successive memory contents (i, t).
• Modifying Memory: The contents of a specific address can be changed by typing new octal digits (c).
• Searching Registers: TYC can search for and display registers containing specific octal values (f).
• Executing Instructions: Users can type and execute specific octal instructions (e). TYC manages the saving and restoring of AC and IO registers during execution and allows for continuous execution of instructions if Sense Switch 1 is active.
• Defining Custom Commands: New single-character commands can be defined to execute frequently used or complex octal instructions (d), streamlining debugging and control.

TYC also provides several subroutines that can be called by other programs, such as getl (to get a typed character), getn (to read 'n' octal digits as a computer word), and type (to print a word in octal).

Recent modifications have introduced advanced features for block manipulation and comparison:

• Parameter Setting: Commands (xa-β-γ-) to set beg, end, and new parameters (octal numbers representing register addresses or values).
• Register Block Copying: A command (y) to copy the contents of registers from a specified beg to end address into another block of registers starting at new.
• Register Block Comparison: A command (z) to compare the contents of the beg to end block with the new block, printing any differences. This feature is particularly useful for analyzing the state of memory before and after a program has executed.