2024-10-19 11:00:03 +01:00
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---
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tags: [CPU]
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---
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# The Little Man Computer
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The [Little Man Computer]() is a simplified computer that works on Von Neuman
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principles. It has all the CPU components we have detailed above. It is
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programmed in machine code but for simplicity it uses the denary rather than the
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binary number system.
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2024-10-20 19:50:20 +01:00
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2024-10-19 11:00:03 +01:00
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On the left is the instruction set. Each number constitutes and execution
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routine and the `xx` stand for the address in RAM that the execution will work
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on.
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Each row of the RAM has a denary address, 1 through to 99. Each address can hold
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three digits.
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- So the instruction `560` would mean _load the number at address 60._
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- The instruction `340` would mean _store a datum at address 40_
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### Working through a basic computation
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We are going to add two numbers together as a basic example.
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1. First we need to place the two numbers in RAM we are going to use `5` and `3`
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- At address `60` we will put the number `5` and at address `61` we will put
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the number `3`
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- We are going to start at address `0` in the top left of the RAM grid
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1. The first instruction will be _load address 60_ which in the assembly will be
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`560` . We put this in address `0`, our starting point.
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1. This first instruction is now stored in the accumulator.
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1. Now we want to _add this number (in the accumulator) to the number in address
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61_
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1. This second instruction is `161` . We write this in address `1`
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1. Finally we want to store the output of the calculation in the RAM, let's say
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at address `62`
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1. So we store the command `362` at address `2`
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