Assignment 3 consists of 1) Symbol table handling and 2) Generating an assembly code for
Rat20SU.
Some Semantics:
• Consider that “true” has an integer value of 1 and “false” has an integer value of 0.
• No arithmetic operations are allowed for booleans.
• The types must match for arithmetic operations (no conversions)
Part 1) Symbol table Handling (3 points): Every identifier declared in the program should
be placed in a symbol table and accessed by the symbol table handling procedures.
a) Each entry in the symbol table should hold the lexeme, and a “memory address” where an
identifier is placed within the symbol table. For example, define a global integer variable called
“Memory_address” and set initially 5000 and increment it by one when a new identifier is
declared and placed into the table.
b) You need to write a procedure that will check to see if a particular identifier is already in the
table, a procedure that will insert into the table and a procedure that will printout all identifiers in
the table. If an identifier is used without declaring it, then the parser should provide an error
message. Also, if an identifier is already in the table and wants to declare it for the second time,
then the parser should provide an error message. Also, you should check the type match.
Part 2) Generating the assembly code (12 points):
Add code (See the partial solution) to your parser that will produce the assembly code
instructions. The instructions should be kept in an array and at the end, the content of the array is
printed out to produce the listing of assembly code. Your array should hold at least 300 assembly
instructions. The instruction starts from 1.
The listing should include an array index for each entry so that it serves as label
to jump to. The compiler should also produce a listing of all the identifiers.

2
Our target machine is a virtual machine based on a stack with the following instructions
I1. PUSHI {Integer Value} Pushes the {Integer Value} onto the Top of the Stack (TOS)
I2. PUSHM {ML – Memory Location} Pushes the value stored at {ML} onto TOS
I3. POPM {ML} Pops the value from the top of the stack and stores it at {ML}
I4. STDOUT Pops the value from TOS and outputs it to the standard output
I5. STDIN Get the value from the standard input and place in onto the TOS
I6. ADD Pop the first two items from stack and push the sum onto the TOS
I7. SUB Pop the first two items from stack and push the difference onto the TOS
( Second item – First item)
I8. MUL Pop the first two items from stack and push the product onto the TOS
I9. DIV Pop the first two items from stack and push the result onto the TOS
( Second item / First item and ignore the remainder)
I10. GRT Pops two items from the stack and pushes 1 onto TOS if second item is
larger otherwise push 0
I11. LES Pops two items from the stack and pushes 1 onto TOS if the second item is
smaller than first item otherwise push 0
I12. EQU Pops two items from the stack and pushes 1 onto TOS if they are equal
otherwise push 0
I13. JUMPZ {IL – Instruction Location} Pop the stack and if the value is 0 then jump to {IL}
I14. JUMP {IL} Unconditionally jump to {IL}
I15. LABEL Empty Instruction; Provides the instruction location to jump to.
A Sample Source Code
$$
[* declarations *]
integer i
integer max;
integer sum;
sum = 0;
i = 1;
get ( max);
while (i < max) {
sum = sum + i;
i = i + 1;
}
sum = sum + max;
put (sum);
$$
3
One Possible Assembly Code Listing
1 PUSHI 0
2 POPM 5002
3 PUSHI 1
4 POPM 5000
5 STDIN
6 POPM 5001
7 LABEL
8 PUSHM 5000
9 PUSHM 5001
10 LES
11 JUMPZ 21
12 PUSHM 5002
13 PUSHM 5000
14 ADD
15 POPM 5002
17 PUSHM 5000
17 PUSHI 1
18 ADD
19 POPM 5000
20 JUMP 7
21 PUSHM 5002
22 PUSHM 5001
23 ADD
24 POPM 5002
25 PUSHM 5002
24 STDOUT