Single Precision Decimal-to-Binary Conversion and Input ASR 33, Signed or Unsigned

This document describes a PDP-8 software subroutine designed to convert a string of up to four decimal digits entered via a Teletype ASR 33 keyboard into its corresponding 2's complement binary representation.

Key features of the routine include:

• Input Handling: It accepts digits 0–9 and can process signed (positive or negative) or unsigned inputs. A space, plus, or minus sign may precede the digits.
• Editing: The routine supports a "back arrow" key to allow the operator to erase and re-enter values during input.
• Conversion Logic: It uses a mathematical approach to shift and add values, processing decimal digits into a binary format.
• Operational Requirements: The routine requires 74 core locations, is invoked via a JMS instruction, and should not be used while the interrupt is active.
• Constraints: The input is restricted to a maximum of 4 decimal digits, with specific input range limits depending on whether the number is signed (±2047) or unsigned (4095).

The documentation provides the full assembly source code, a program flow chart, and explanations of the loading procedure and calling sequence.