Little Man Program Code
LMC Instruction Set LMC Instruction Set The LMC has nine instructions. Each instruction has an assembly mnemonic that is equivalent to a three-digit (decimal) instruction. In this numerical instruction, the first digit usually represents the instruction, and the second and third digits usually represent a mailbox address. LOAD mnemonic - LDA numerical/machine code - 5 Load the contents of the given mailbox onto the accumulator (calculator). Note: the contents of the mailbox are not changed. STORE mnemonic - STA numerical/machine code - 3 Store the contents of the accumulator (calculator) to the mailbox of the given address.
Little Man Program Examples
Note: the contents of the accumulator are not changed. ADD mnemonic - ADD numerical/machine code - 1 Add the contents of the given mailbox onto the accumulator (calculator).
Note: the contents of the mailbox are not changed, and the actions of the accumulator are not defined for add instructions that cause sums larger than 3 digits. SUBTRACT mnemonic - SUB numerical/machine code - 2 Subtract the contents of the given mailbox from the accumulator (calculator). Note: the contents of the mailbox are not changed, and the actions of the accumulator are not defined for subtract instructions that cause negative results - however, a negative flag will be set so that BRP can be used properly (see below). INPUT mnemonic - INP numerical/machine code - 901 Copy the value from the 'in box' onto the accumulator (calculator). OUTPUT mnemonic - OUT numerical/machine code - 902 Copy the value from the accumulator (calculator) to the 'out box'. Note: the contents of the accumulator are not changed. END mnemonic - HLT numerical/machine code - 000 Causes the Little Man Computer to stop executing your program.
Little Man Program Code 10
SELECT or enter a program, LOAD a file or alter memory SELECT add add/subtr ascii ascii table OPTIONS clear memory show op codes show decimal hide op codes default fast default normal default slow.
BRANCH IF ZERO mnemonic - BRZ numerical/machine code - 7 If the contents of the accumulator (calculator) are 000, the PC (program counter) will be set to the given address. Note: since the program is stored in memory, data and program instructions all have the same address/location format. BRANCH IF ZERO OR POSITIVE mnemonic - BRP numerical/machine code - 8 If the contents of the accumulator (calculator) are 000 or positive (i.e. The negative flag is not set), the PC (program counter) will be set to the given address. Note: since the program is stored in memory, data and program instructions all have the same address/location format.
Little Man Program Code
BRANCH ALWAYS mnemonic - BRA numerical/machine code - 6 Set the contents of the accumulator (calculator) to the given address. Note: since the program is stored in memory, data and program instructions all have the same address/location format. DATA LOCATION mnemonic - DAT numerical/machine code - (the data) When compiled, a program converts each instruction into a three-digit code.
These codes are placed in sequential mailboxes. Instead of a program component, this instruction will reserve the next mailbox for data storage.