1. MIC-1 SIMULATOR Programming in IJVM
Computer Architecture
Jim Skon

2. Topics Mic-1 simulator programming Reverse Polish notation
Programming assignment on Moodle
Reverse Polish notation
Assembly language
IJVM instruction set

3. Using the Mic-1 Simulator
Runs as a Java Application
Simulates a simplified version of the Java Virtual Machine.
Can be Downloaded from Moodle.
Two Versions
High resolution
Low resolution

4. Using the Mic-1 Simulator
Write IJVM “.jas” files using an editor – (
Start the Mic-1 simulator
Load and Assemble the “.jas” file using the IJVM assembler. Use the “File/Assemble/ Load JAS file.”
This creates machine code.
Program is ready to run.
Example: acsii.jas
Prints all characters!

5. Reverse Polish Notation (RPN)
Method to write arithmetic expressions
Avoids the use of brackets to define priorities for evaluation of operators
Devised by Jan Lucasiewicz
Polish philosopher and mathematician
In his notation, the operators preceded their arguments
The “reverse” places operators after arguments
For more info
stone.ch.cam.ac.uk/documentation/rrf/rpn.ht ml
tation

6. RPN Example (3 + 5) * (7 -2) Add 3 to 5 Then, subtract 2 from 7
Finally, multiply the two results together
Using RPN notation: *

7. RPN Example – Stack based
* (read from left to right)
Push 3 onto stack
Push 5 onto the stack – The stack now contains (3, 5)
Use “+” operator – Pop two numbers from stack and push result (8)
Push 7 onto the stack
Push 2 onto the stack – The stack now contains (8, 7, 2)
Use “-” operator – Pop two numbers from stack and push result (5)
Use “*” operator – Pop two numbers from stack and push result (40)

8. RPN Example – IJVM Code BIPUSH 3
BIPUSH 5 – The stack now contains (3, 5)
IADD – Pop two numbers from stack and push result (8)
BIPUSH 7
BIPUSH 2 – The stack now contains (8, 7, 2)
ISUB – Pop two numbers from stack and push result (5)
IMUL – Pop two numbers from stack and push result (40)

9. Structured Computer Organization
Digital logic builds microarchitecture
Microarchitecture implements the ISA
ISA is in machine language
Assembly language allows us to use ISA

10. Assembly Language
Uses symbolic names (mnemonics) and symbolic addresses (variables) for the machine language
An assembler converts the assembly language into machine language
Each statement produces exactly one machine instruction (1:1 mapping)

11. Why Use Assembly? Versus machine language Versus high-level language
Easier to remember mnemonics for instructions instead of corresponding machine language
Easier to work with the symbolic addresses instead of numerical values of address
Versus high-level language
Access: has access to all features and instructions of the ISA
Performance: Code produced can be much smaller (for low-memory devices) and faster (for speed-critical functions)

12. Undocumented Assembler Instructions
ARG : Agree to Run Garbage
BDM : Branch and Destroy Memory
CMN : Convert to Mayan Numerals
DDS : Damage Disk and Stop
EMR : Emit Microwave Radiation
ETO : Emulate Toaster Oven
FSE : Fake Serious Error
GSI : Garble Subsequent Instructions
GQS : Go Quarter Speed
HEM : Hide Evidence of Malfunction
IDD : Inhale Dust and Die
IKI : Ignore Keyboard Input

13. IJVM Instruction Set

14. IJVM Instruction Set

15. Exercise Write IJVM assembly code for the following C++ code:
int x = 0;
for (int i = 0; i < 20; i++)
x+= i;

16. Basic Program Format
.main // all variables declared within .varand .end-var .var x i .end-var // Main program goes next // Program execution is terminated with a HALT statement // See next slide for exercise solution .end-main

17. Solution to Previous Exercise
BIPUSH 0 ISTORE x ISTORE I L1: BIPUSH 19 ILOAD i ISUB IFLT L2 ILOAD x IADD IINC i 1 GOTO L1 L2: HALT

18. Input and Output IN OUT Reads a character from the key buffer
Pushes its value onto the stack
If no key has been pressed, zero will be pushed onto the stack
OUT
Pops a word off the stack
Prints it to the standard output text area
Can only output ASCII values

19. Getting a Character from Keyboard
GOTO getch L0: ISTORE z HALT getch: IN DUP IFEQ reread GOTO L0 reread: POP

20. Assignment
Get the ascii.jas, sum.jas, and echo.jas programs to all work.
Write a program to read in a two digit number, and sum the even numbers from 2 to that number.
Extra credit if you can print out the answer.