1. Making Programming Friendlier
LMC Assembly
Making Programming Friendlier

2. Machine Code Issues Have to remember numeric opcodes
Have to think about physical memory locations
Machine code
901 1
307 2
506 3
207 4
902 5
000 6
010 7 8 9

3. Machine Code Issues Have to remember numeric opcodes
Have to think about physical memory locations
What if I need to add 6 lines of code to this program?
Machine code
901 1
307 2
506 3
207 4
902 5
000 6
010 7 8 9

4. Machine Code Issues Have to remember numeric opcodes
Have to think about physical memory locations
What if I need to add 6 lines of code to this program?
Machine code
901 1
307 2
506 3
207 4
NEW 5 6
902 7
000 8
010 9

5. Assembly
Assembly Code : human readable machine code

6. Assembly Little Man Computer Assembly: Assembly Machine code INP 901
INP
901 1
STA FIRST
307 2
LDA TEN
506 3
ADD FIRST
107 4
OUT
902 5
HLT
000 6
TEN DAT 10
010 7
FIRST DAT 0
Assembly
Machine code
Instruction
HLT
000
end (halt)
ADD
1xx
add
SUB
2xx
subtract
STA
3xx
store
STore Accumulator value
LDA
5xx
load
LoaD into Accumulator
BRA
6xx
branch always
BRanch Always
BRZ
7xx
branch if 0
BRanch if Zero
BRP
8xx
branch if >= 0
BRanch if zero or Positive
INP
901
input
OUT
902
output
DAT
data location
Used to specify a memory location

7. DAT DAT Value: "this location is data" Value is placed into memory HLT5
HLT
000 6
TEN DAT 10
010 7
FIRST DAT 0

8. Identifier Identifier : Name for a memory location
Can come before any instruction
IDENTIFIER INSTRUCTION … 5
HLT
000 6
TEN DAT 10
010 7
FIRST DAT 0

9. No XX Assembly can use names for memory locations Assembly
Machine code
INP
901 1
STA FIRST
307 2
LDA TEN
506 3
SUB FIRST
207 4
OUT
902 5
HLT
000 6
TEN DAT 10
010 7
FIRST DAT 0

10. Names And Branch Use as target of branch:
#1 This is called LOOPSTART We add one to accumulator
#3 Branch to the instruction named LOOPSTART
Assembly
LDA ZERO 1
LOOPSTART ADD ONE 2
OUT 3
BRA LOOPSTART 4
HLT 5
ZERO DAT 0 6
ONE DAT 1

11. Named Locations Named locations not affected by adding/removing code
Ex: Add EXTRA lines
Assembly fine
Machine version broken
Assembly
Machine code
INP
901 1
STA FIRST
307 2
LDA TEN
506 3
SUB FIRST
207 4
EXTRA 5 6
OUT
902 7
HLT
000 8
TEN DAT 10
010 9
FIRST DAT 0

12. Assembler An Assembler converts assembly to machine code: