I personally find reading this a little confusing but it says it's a super simple machine language program. However, this is what I'm saying about how confusing all this would be when you don't have all the rules written down in this format and all you might be finding is zeros and ones. So, the structure of what someone is doing would be completely missing and only the computers would know because the language would be missing (computer language). So, the effect without some kind of human translating device would be something as alien as a UFO language in some ways. 

begin quote from:

https://courses.cs.washington.edu/courses/cse378/02sp/sections/section2-2.html

An Example Super Simple Machine Program 

An Example Super Simple Machine Program

Problem

Write a machine code program to write zeros into memory. The start address is given at address 0x80 and the number of words to write is given at address 0x84. We assume the start address is word aligned and the number of words to write is greater than zero.

Pseudocode (optional)

Write out each step your assembly language program needs to do. You can skip this if you find yourself writing assembly code.

R0 = 0x80              (address of start address)
R0 = memory[R0]        (current address)
R1 = 0x84              (address of number of words)
R1 = memory[R1]        (number of words)
R2 = 0x0               (constant 0)
R3 = 0x4               (constant 4)
R4 = 0x0               (number of words written to)
R5 = 0x1               (constant 1)
store R2 in memory[R0]
R0 = R0 + R3
R4 = R4 + R5
if (R4 != R1) branch to the store instruction (address 0x20)

Assembly Code

Translate the pseudocode from above if necessary into assembly code.

IMM   R0,   0x80
LOAD  R0,   R0
IMM   R1,   0x84
LOAD  R1,   R1
IMM   R2,   0x0
IMM   R3,   0x4
IMM   R4,   0x0
IMM   R5,   0x1
STORE R0,   R2
ADD   R0,   R0, R3
ADD   R4,   R4, R5
BNE   0x20, R4, R1

Machine Code

Translate the assembly code into machine code using this chart:

Operation	Opcode	Meaning of other bytes
ADD	0x20	Dest. reg.	Reg. 1	Reg. 2
IMM	0x60	Dest. reg.	Unused	Value
BNE	0x11	Dest. address	Reg. 1	Reg. 2
LOAD	0xA4	Dest. reg.	Reg. with address	Unused
STORE	0x08	Unused	Reg. with dest. address	Source reg.

0x 60 00 00 80
0x A4 00 00 00
0x 60 01 00 84
0x A4 01 01 00
0x 60 02 00 00
0x 60 03 00 04
0x 60 04 00 00
0x 60 05 00 01
0x 08 00 00 02
0x 20 00 00 03
0x 20 04 04 05
0x 11 20 04 01

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CSE 378 Spring 2002 - Section 2

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