I searched for the document but cannot provide the PDF directly, as it is a restricted U.S. Army training circular. However, I can write a feature article about the document—its purpose, contents, and role in Army crew training. Feature: Mastering the Battlefield – Inside TC 3-20.31, the Army’s Blueprint for Crew Training and Qualification In the high-stakes world of armored and mounted combat, a vehicle is only as effective as its crew. The U.S. Army’s TC 3-20.31, “Training and Qualification – Crew” serves as the definitive manual for building, certifying, and sustaining lethal, disciplined crews across fighting vehicles like the M1 Abrams, M2 Bradley, and Stryker family. The Core Mission of TC 3-20.31 Published under the Directorate of Training and Doctrine (TRADOC), TC 3-20.31 standardizes how crews train, from gunnery skills to tactical decision-making. Unlike higher-level field manuals focused on battalion maneuvers, this circular drills down to the individual crew station—driver, gunner, commander, and loader (if applicable).
This LMC simulator is based on the Little Man Computer (LMC) model of a computer, created by Dr. Stuart Madnick in 1965. LMC is generally used for educational purposes as it models a simple Von Neumann architecture computer which has all of the basic features of a modern computer. It is programmed using assembly code. You can find out more about this model on this wikipedia page.
You can read more about this LMC simulator on 101Computing.net.
Note that in the following table “xx” refers to a memory address (aka mailbox) in the RAM. The online LMC simulator has 100 different mailboxes in the RAM ranging from 00 to 99.
| Mnemonic | Name | Description | Op Code |
| INP | INPUT | Retrieve user input and stores it in the accumulator. | 901 |
| OUT | OUTPUT | Output the value stored in the accumulator. | 902 |
| LDA | LOAD | Load the Accumulator with the contents of the memory address given. | 5xx |
| STA | STORE | Store the value in the Accumulator in the memory address given. | 3xx |
| ADD | ADD | Add the contents of the memory address to the Accumulator | 1xx |
| SUB | SUBTRACT | Subtract the contents of the memory address from the Accumulator | 2xx |
| BRP | BRANCH IF POSITIVE | Branch/Jump to the address given if the Accumulator is zero or positive. | 8xx |
| BRZ | BRANCH IF ZERO | Branch/Jump to the address given if the Accumulator is zero. | 7xx |
| BRA | BRANCH ALWAYS | Branch/Jump to the address given. | 6xx |
| HLT | HALT | Stop the code | 000 |
| DAT | DATA LOCATION | Used to associate a label to a free memory address. An optional value can also be used to be stored at the memory address. |