The load (LOAD) instruction copies a value from one memory cell to another.

The LOAD instruction format is:

load dst=destination addr=address imm=immediate

The value at memory cell #source is copied to destination, where source is the value in memory cell #address + immediate.

Here is an example:

Instruction #0 is a LOAD instruction. dst is 5, so the destination is cell #5. addr is 1, but this does NOT mean that the source is cell #1. Rather, the source is the value of cell #1, which is 3, plus the immediate. But imm is 0, so the source is cell #3. Thus, the computer copies the value of cell #3, which is 7, to cell #5.

More generally, if the following are true:

• the PC at time t = i
• instruction #i is load dst=dst addr=addr imm=imm

Then we can conclude the following:

• value of cell dst at time (t + 1) = value of cell ((value of cell addr at time t) + imm) at time t
• the PC at time (t + 1) = x + 1

As we can see, the PC increases by 1. Also, memory cells other than the destination are not affected by this instruction.

For example, if the following are true:

• the PC at time 0 = 0
• instruction #0 is load dst=5 addr=1 imm=0
• value of cell 1 at time 0 = 3
• value of cell 3 at time 0 = 7

Then we can conclude the following:

• value of cell 5 at time (0 + 1) = value of cell ((value of cell 1 at time 0) + 0) at time 0
• the PC at time (0 + 1) = 0 + 1

Value of cell #1 is 3, so the first conclusion reduces to:

value of cell 5 at time (0 + 1) = value of cell (3 + 0) at time 0

This simplifies to:

value of cell 5 at time 1 = value of cell 3 at time 0

Since the value of cell 3 is 7, we conclude that:

value of cell 5 at time 1 = 7

We can also simplify the second conclusion to:

the PC at time 1 = 1