Binary-to-Binary-Coded-Decimal Conversion (Four Digit)

This document details a subroutine for the PDP-8 computer designed to convert binary integers (ranging from 0 to 4095) into four binary-coded-decimal (BCD) characters packed into two computer words. This program is an extension of the previously released Digital-8-14-U-Sym, allowing for the handling of larger integers.

Key Technical Details:

• Requirements: The subroutine occupies 53 (decimal) storage locations and is intended for use on a standard PDP-8 system.
• Usage: It is invoked via the JMS instruction, with the binary number provided in the accumulator.
• Execution Time: Performance varies between 304.5 and 328.5 microseconds.
• Format: The output format is optimized for IBM-compatible magnetic tape recording, although specific auxiliary routines may be required to adjust parity or substitute specific character codes (such as changing 0000 to 1010 for zero) to meet specific IBM BCD compatibility standards.

The document concludes by providing the full assembly language source code listing and memory map for the implementation.