Assembly Language

Friday, Week 5

Monday, Week 6

Assembly Language

Set of mnemonic names for the instructions in a particular computer's machine language.

Works on accumulator and memory locations in the computer.

Translated into binary instructions.

Pippin

STO X Store accumulator value in memory location X

LOD X Load contents of memory location X into accumulator

LOD #X Load value X into accumulator

HLT Halt execution

ADD X Add contents of memory location X to accumulator

ADD #X Add value X to accumulator

Pippin

Pippin has an accumulator - a place to store intermediate values during computation.

Similar to the calculator but we have memory locations to store values and to load values.

Sample Program

LOD #2

STO 129

ADD 129

STO 129

ADD #3

STO 130

HLT

Exercise

What would be the assembly instructions to add 1 to the contents of memory location 130?

STO XStore acc value in mem loc X

LOD XLoad contents of mem loc X into acc

LOD #X Load value X into acc

HLT Halt execution

ADD X Add contents of mem loc X to acc

ADD #X Add value X to acc

Exercise Solution

LOD #1

ADD 130

STO 130

HLT

Exercise

What would be the assembly language instructions to add the values in memory locations 129 and 132, putting the answer in 128?

STO XStore acc value in mem loc X

LOD XLoad contents of mem loc X into acc

LOD #X Load value X into acc

HLT Halt execution

ADD X Add contents of mem loc X to acc

ADD #X Add value X to acc

Exercise Solution

LOD 129

ADD 132

STO 128

HLT

Machine Language

Assembly language still cannot be read directly by the computer - it’s not in binary.

Assembly language commands need to be translated into binary commands called machine language.

Pippin Machine Language

LOD X 00000100

LOD # 00010100

ADD X 00000000

ADD # 00010000

STO 00000101

HLT 00001111

Memory location 129 10000001

Memory location 130 10000010

Example Program

LOD 129 00000100 10000001

ADD #3 00001000 00000011

STO 129 00000101 10000001

HLT 00001111

Exercise

LOD X

ADD Y

STO Y

HLT

LOD X

LOD #

ADD X

ADD #

STO

HLT

00000100

00010100

00000000

00010000

00000101

00001111

Translate above into machine language.

Memory location X

Memory location Y

10000001

10000010

Exercise Solution

LOD X

ADD Y

STO Y

HLT

00000100

00000000

00000101

00001111

10000001

10000010

10000010

Exercise

Write an assembly program that calculates Y=X+3.

LOD X

LOD #

ADD X

ADD #

STO

HLT

00000100

00010100

00000000

00010000

00000101

00001111

Translate the program into machine language.

Memory location X

Memory location Y

10000001

10000010

Exercise Solution

LOD X

ADD #3

STO Y

HLT

00000100

00010000

00000101

00001111

10000001

00000011

10000010

PIPPIN Lab

This week’s lab will be to use a simulator called PIPPIN to write assembly language programs and change them to machine language.

Let’s take a look at PIPPIN. Do Pre-Lab Assignment

JMP

All commands seen so far in PIPPIN are sequential.

We have no way to make a decision or to skip some statements.

JMP X command says always jump to the command labeled X.

JMZ X checks the accumulator first - if it’s 0 then we jump; otherwise don’t jump.

Example

LOD #3

STO X

LOD #0

STO Z

LOOP: LOD Z

ADD Y

STO Z

LOD X

SUB #1

STO X

JMZ END

JMP LOOP

END: LOD Z

STO Y

HLT

In JavaScript

The same program in JavaScript would be the following:

var z=0;for (var x=3; x!=0; x--)

z += y;y = z;

Or the following:y = y*3;