Machine

1
Machine Assembly Language
2
Machine Language

• Computer languages cannot be read directly by the
  computer they are not in binary.
• All commands need to be translated into binary
  instructions called machine language.
• Each type of CPU has its own machine language.

3
Von Neumann Architecture
Memory
CPU
Control Unit
Registers
ALU
4
Slightly More Complete Picture
Memory
CPU
Control Unit
Registers
ALU
Secondary Storage
5
Von Neumann Architecture

• Program and Data are both stored in memory.
• Fetch, Decode, Execute cycle

6
Machine Language

• We will look at a simulated CPU provided by the
  author of our book
• This machine language has only 12 different
  instructions
• Each instruction is 16 bits long.
• Data values are also limited to 16 bits.

7
Sample Instruction
Instruction ID
Register
Memory Location
8
Machine Language
9
Machine Language
10
Sample Machine Language Program

• Add the contents of register 1 to the contents of
  register 2 and store it in register 0
• 1010000100 00 01 10
• 1111111111111111

11
Sample Machine Language Program

• Add the contents of memory location 1 to the
  contents of register 2 and store it in register
  0
• 100000010 01 00001
• 1010000100 00 01 10
• 1111111111111111

12
Assembly Language

• Set of mnemonic names for the instructions in a
  particular computer's machine language.
• Works on registers and memory locations in the
  computer.
• Translated into binary instructions.

13
Assembly Language
14
Assembly Language
15
Sample Assembly Language

• Add the contents of register 1 to the contents of
  register 2 and store it in register 0
• ADD R0 R1 R2
• HALT

16
Sample Machine Language

• Add the contents of memory location 1 to the
  contents of register 2 and store it in register
  0
• LOAD R1 1
• ADD R0 R1 R2
• HALT

17
Sample Program

• LOAD R2 5
• ADD R2 R2 R2
• LOAD R1 3
• ADD R3 R1 R2
• HALT
• What does this program do?

18
Exercise

• What would be the assembly instructions to swap
  the contents of registers 1 2?

• STORE MEM REG
• LOAD REG MEM
• MOVE REG REG
• ADD REG REG REG
• SUB REG REG REG
• HALT

19
Exercise Solution

• STORE 1 R1
• MOVE R1 R2
• LOAD R2 1
• HALT

20
Exercise

• What would be the assembly instructions to do
  the following computation
• R0 Mem7 R2 - R3

• STORE MEM REG
• LOAD REG MEM
• MOVE REG REG
• ADD REG REG REG
• SUB REG REG REG
• HALT

21
Exercise Solution

• SUB R2 R2 R3
• LOAD R1 7
• ADD R0 R1 R2
• HALT
• (we want R0 Mem7 R2 - R3)

22
Some More Instructions

• We are missing some crucial functionality
• ??

23
Some More Instructions

• We are missing some crucial functionality
• Loops!

24
A More Complex Example
25
In Python

• The same program in Python would be the
  following
• z 0
• x 3
• while x ! 0
• z y
• x x -1
• y z
• Or the following
• y y3

26
Compilers, Interpreters, Assemblers

• Because it is not fun to program in Assembly, we
  have high level programming languages.
• Python
• Alice
• C, C, Java, Fortran, Cobol, Pascal, C, M,
  Ada, lisp, Ruby, Smalltalk, C,
• Compiler/Interpreter translates from the
  high-level language to machine language.

27
Program Translation
z 0 x 3 while x ! 0 z y x
x -1 y z
1010000100000110 1010001000000110 0000001000000100
0000000100000000 1001000100001011
1111111111111111
Compiler
Assembler