Little Man Computer – Max Function

LMC-MaxIn this challenge we will create a computer program using LMC (Little Man Computer) that takes two inputs and outputs the larger (max) of the the two inputs.

By completing this challenge we will investigate the use of the branching instructions BRP and BRA to create an IF THEN ELSE selection.

Flowchart


We have produced the flowchart of our max algorithm using LMC instructions:
LMC_Flowchart_Max

LMC Simulator


You can now type and test this code using the Online LMC Simulator.

LMC Instruction Set


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.
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