1. LET’S MAKE UP A LANGUAGE
000000
op-code operand Control Unit
Instruction Pointer
INSTRUCTION EXPLANATION
000XXX Load the value located at memory
location XXX into the register
001XXX Put the value of register at memory ALU
location XXX
010XXX Add XXX to the value of register
Register
011XXX Subract XXX from the value of
register
111XXX End program
1

2. INSTR EXPL
START PROGRAM
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110
001 010001
000
010 001111
011 111000
100
101
110 000001
111
2

3. INSTR EXPL
FETCH INSTRUCTION
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 000110
001 010001
000
010 001111
011 111000
100
101
110 000001
111
3

4. INSTR EXPL
DECODE
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE Load value
000 000110 000110 located at
memory location
001 010001
110 into register
000
010 001111
011 111000
100
101
110 000001
111
4

5. INSTR EXPL
EXECUTE
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 000110
001 010001
000
010 001111
011 111000
100
Load from 110
101
110 000001 000001
111
5

6. INSTR EXPL
INCREMENT IP
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110
001 010001 Increment
001 instruction
010 001111
pointer
011 111000
100
101
110 000001 000001
111
6

7. INSTR EXPL
FETCH INSTRUCTION
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 010001
001 010001
001
010 001111
011 111000
100
101
110 000001 000001
111
7

8. INSTR EXPL
DECODE
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 010001 Add 001 to the
value of
001 010001
register
001
010 001111
011 111000
100
101
110 000001 000001
111
8

9. INSTR EXPL
EXECUTE
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 010001
001 010001
001
010 001111
011 111000
100
Add 001 to register
101
110 000001 000010
111
9

10. INSTR EXPL
INCREMENT IP
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110
001 010001 Increment
010 instruction
010 001111
pointer
011 111000
100
101
110 000001 000010
111
10

11. INSTR EXPL
FETCH INSTRUCTION
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 001111
001 010001
010
010 001111
011 111000
100
101
110 000001 000010
111
11

12. INSTR EXPL
DECODE
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
Put value of
000 000110 001111 register at
001 010001 memory
010 location 111
010 001111
011 111000
100
101
110 000001 000010
111
12

13. INSTR EXPL
DECODE
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 001111
001 010001
010
010 001111
011 111000
100 Put value of register at
101 111
110 000001 000010
111 000010
13

14. INSTR EXPL
INCREMENT IP
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110
001 010001 Increment
011 instruction
010 001111
pointer
011 111000
100
101
110 000001 000010
111 000010
14

15. INSTR EXPL
FETCH INSTRUCTION
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 111000
001 010001
011
010 001111
011 111000
100
101
110 000001 000010
111 000010
Chapter 1: Computers and Digital Basics 15

16. INSTR EXPL
DECODE
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110 111000 End Program
001 010001
011
010 001111
011 111000
100
101
110 000001 000010
111 000010
Chapter 1: Computers and Digital Basics 16

17. INSTR EXPL
INCREMENT IP
000XXX Load XXX into REG
001XXX Put REG into location XXX
010XXX Add XXX to REG
011XXX Subtract XXX from REG
111XXX End program
ADDR VALUE
000 000110
001 010001 What would happen if the last instruction
010 001111 would write to 011 instead of 111?
011 111000
100
101
110 000001 What would I set the instruction pointer to
110 instead to 000 at the beginning of the
111 000010
exercise?
17