MIC-1 SIMULATOR
Programming in IJVM
Computer Architecture
Jim Skon
Topics
Mic-1 simulator programming
◦ http://www.ontko.com/mic1/
◦ Programming assignment on Moodle
Reverse Polish notation
Assembly language
IJVM instruction set
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
Using the Mic-1 Simulator
Write IJVM “.jas” files using an editor –
(www.textpad.com)
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!
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
http://wwwstone.ch.cam.ac.uk/documentation/rrf/rpn.ht
ml
http://en.wikipedia.org/wiki/Reverse_Polish_No
tation
RPN Example
(3 + 5) * (7 -2)
Add 3 to 5
Then, subtract 2 from 7
Finally, multiply the two results together
Using RPN notation: 3 5 + 7 2 -*
RPN Example – Stack based
3 5 + 7 2 -* (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)
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)
Structured Computer Organization
Digital logic builds
microarchitecture
Microarchitecture
implements the ISA
ISA is in machine
language
Assembly language
allows us to use ISA
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)
Why Use Assembly?
Versus machine 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)
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
IJVM Instruction Set
IJVM Instruction Set
Exercise
Write IJVM assembly code for the
following C++ code:
int x = 0;
for (int i = 0; i < 20; i++)
x+= i;
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
Solution to Previous Exercise
BIPUSH 0
ISTORE x
BIPUSH 0
ISTORE I
L1: BIPUSH 19
ILOAD i
ISUB
IFLT L2
ILOAD x
ILOAD i
IADD
ISTORE x
IINC i 1
GOTO L1
L2: HALT
Input and Output
IN
◦ 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
Getting a Character from Keyboard
GOTO getch
L0:
ISTORE z
HALT
getch: IN
DUP
IFEQ reread
GOTO L0
reread: POP
GOTO getch
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.
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