Memory Address Test

This document describes MAINDEC-9A-DOCA-D, a Memory Address Test designed for the PDP-9 computer. Its core function is to verify the integrity of the 8K memory system by ensuring that all memory locations not used by the program can be uniquely addressed, that every bit within a memory word is accessible for writing and reading, and that memory locations are not inadvertently shorted together.

The program comprises four main tests:

1. Individual Location Test: Writes a memory location's address into itself, followed by its complement, and then verifies the data.
2. Forward Write-Read Test: Sequentially writes addresses into memory locations in a forward direction and then reads them back to confirm they contain their own addresses.
3. Reverse Complement Write-Read Test: Writes the complement of sequential addresses into memory locations in reverse order (from highest to lowest) and checks for correctness.
4. Write 1's in a Field of 0's Test: This test primarily checks for short circuits between memory bits by writing all 1s into specific locations within an otherwise zero-filled memory field.

The program requires a standard PDP-9 computer with 8K memory. It occupies memory locations 17200 to 17777 and tests all locations below 17200. Operators can control the test's behavior (e.g., halting on error, printing errors, ringing a bell, looping tests) via accumulator switch settings. Errors are typically indicated on the teleprinter. The fourth test has an execution time of approximately 20 minutes, while the others are "insignificant."