Program takes a programming language called 'Simple', converts it to Simple Machine Language (SML), then executes it.
SML
The machine language syntax is a 4 digit number, where the leading two digits describe the operation and the trailing two digits describe the location in memory of which to run the operation against.
OPERATION CODES:
- Input/Output operations:
- READ = 10; WRITE = 11;
- Load and store operations:
- LOAD = 20; STORE = 21;
- Arithmetic operations:
- ADD = 30; SUBTRACT = 31; DIVIDE = 32; MULTIPLY = 33;
- Transfer-of-control operations:
- BRANCH = 40; BRANCHNEG = 41; BRANCHZERO = 42; HALT = 43;
The following program as an example, which reads two numbers from the keyboard and prints their sum.
| Location | Number | Instruction |
|---|---|---|
| 00 | +1007 | Read A |
| 01 | +1008 | Read B |
| 02 | +2007 | Load A |
| 03 | +3008 | Add B |
| 04 | +2109 | Store C |
| 05 | +1109 | Write C |
| 06 | +4300 | Halt |
| 07 | +0000 | Variable A |
| 08 | +0000 | Variable B |
| 09 | +0000 | Result C |
SIMPLE
These are the following acceptable commands for the Simple language. Each statement begins with a line number. The actual value of the line is arbitrary, so long as the lines continue forth in ascending order.
| Command | Example |
|---|---|
| rem | 10 rem this is a remark |
| input | 20 input x |
| let | 30 let a = 1 + (b * 2) |
| 40 print a | |
| goto | 50 goto 60 |
| if...goto | 60 if a == x goto 70 |
| end | 70 end |
Consider the following Simple code as an example, which reads 3 digits from the keyboard and prints the average.
| Simple Program |
|---|
| 10 rem calculate the average of 3 integers |
| 20 input a |
| 30 input b |
| 40 input c |
| 50 let d = (a + b + c) / 3 |
| 60 print the average |
| 70 print d |
| 80 end |
The program will then generate SML code based on the Simple input. Once the SML is generated and evaluated, the appropriate output will be shown to the user.
| Simple Program | SML Location & Instruction | Description |
|---|---|---|
| 10 rem calculate the average of 3 integers | none | rem ignored |
| 20 input a | 00 +1020 | load a into location 20 |
| 30 input b | 01 + 1019 | read b into location 19 |
| 40 input c | 02 +1018 | read c into location 18 |
| 50 let d = (a + b + c) / 3 | 03 +2020 | load a (20) into the accumulator |
| 04 +3019 | add b (19) into the accumulator | |
| 05 +2115 | store result into temporary location 15 | |
| 06 +2015 | load from temporary location 15 | |
| 07 +3018 | add c (18) to accumulator | |
| 08 +2114 | store result into temporary location 14 | |
| 09 +2014 | load from temporary location 14 | |
| 10 +3216 | divide loaded variable by 3 (16) | |
| 11 +2117 | store result into d (16) | |
| 60 rem the average will be printed | none | rem ignored |
| 70 print d | 12 +1117 | output d to screen |
| 80 end | 13 +4300 | terminate execution |
| none | 14 +0000 | memory location for temp variable |
| none | 15 +0000 | memory location for temp variable |
| none | 16 +0000 | memory location for the constant 3 |
| none | 17 +0000 | memory location for variable d |
| none | 18 +0000 | memory location for variable c |
| none | 19 +0000 | memory location for variable b |
| none | 20 +0000 | memory location for variable a |
Project inspired by compiler.pdf