P-code-machine

C implementation of p-code machine, exercise from university

Available Functions

You can read about all these functions here. Note: We use functions in uppercase letters because some of your functions has the same name of C-language keywords. The instruction's format is: name(char[3]) level(int) arg(int)

• LIT (Literals)
• OPR (Operation)
  • RTN (Return) OPR 0 0
  • NEG (Negative) OPR 0 1
  • ADD (Add) OPR 0 2
  • SUB (Subtract) OPR 0 3
  • MUL (Multiply) OPR 0 4
  • DIV (Divide) OPR 0 5
  • MOD (Module) OPR 0 6
  • ODD (Odd) OPR 0 7
  • EQL (Equals) OPR 0 8
  • NEQ (Not equals) OPR 0 9
  • LSS (Less than) OPR 0 10
  • LEQ (Less equals) OPR 0 11
  • GTR (Greater than) OPR 0 12
  • GEQ (Greater equals) OPR 0 13
• LOD (Load)
• STO (Store)
• CAL (Call subroutine)
• INT (Internal)
• JMP (Jump)
• JPC (Conditional Jump)
• WRT (Write)

Compilation

gcc -o pcode pcode.c

Running

./pcode

Examples

Sum 2 numbers

INT 0 5
LIT 0 8
STO 0 3
LIT 0 4
STO 0 4
LOD 0 3 
LOD 0 4
OPR 0 2
END 0 0

Output:
Inst       Level           Arg             Top             Counter         Stack
INT        0               5               0               1               0 0 0 0 0 
LIT        0               8               8               2               0 0 0 0 0 8 
STO        0               3               0               3               0 0 0 8 0 
LIT        0               4               4               4               0 0 0 8 0 4 
STO        0               4               4               5               0 0 0 8 4 
LOD        0               3               8               6               0 0 0 8 4 8 
LOD        0               4               4               7               0 0 0 8 4 8 4 
OPR        0               2               4               8               0 0 0 8 4 12 

Subtract 2 numbers

INT 0 5
LIT 0 8
STO 0 3
LIT 0 4
STO 0 4
LOD 0 3 
LOD 0 4
OPR 0 3
END 0 0

Output:
Inst       Level           Arg             Top             Counter         Stack
INT        0               5               0               1               0 0 0 0 0 
LIT        0               8               8               2               0 0 0 0 0 8 
STO        0               3               0               3               0 0 0 8 0 
LIT        0               4               4               4               0 0 0 8 0 4 
STO        0               4               4               5               0 0 0 8 4 
LOD        0               3               8               6               0 0 0 8 4 8 
LOD        0               4               4               7               0 0 0 8 4 8 4 
OPR        0               3               4               8               0 0 0 8 4 4 

Negate a number

INT 0 2
LIT 0 1
OPR 0 1
END 0 0

Output:
Inst       Level           Arg             Top             Counter         Stack
INT        0               2               0               1               0 0 
LIT        0               1               1               2               0 0 1 
OPR        0               1               -1              3               0 0 -1 

Verify if num 1 > num 2

INT 0 5
LIT 0 5
STO 0 3
LIT 0 4
STO 0 4
LOD 0 3
LOD 0 4
OPR 0 12
END 0 0

Output: (1 at top is true, that is 5>4)
Inst       Level           Arg             Top             Counter         Stack
INT        0               5               0               1               0 0 0 0 0 
LIT        0               5               5               2               0 0 0 0 0 5 
STO        0               3               0               3               0 0 0 5 0 
LIT        0               4               4               4               0 0 0 5 0 4 
STO        0               4               4               5               0 0 0 5 4 
LOD        0               3               5               6               0 0 0 5 4 5 
LOD        0               4               4               7               0 0 0 5 4 5 4 
OPR        0               12              1               8               0 0 0 5 4 1

INT 0 5
LIT 0 8
STO 0 3
LIT 0 9
STO 0 4
LOD 0 3
LOD 0 4
OPR 0 12
END 0 0

Output: (0 at top is false, that is 8<9)
Inst       Level           Arg             Top             Counter         Stack
INT        0               5               0               1               0 0 0 0 0 
LIT        0               8               8               2               0 0 0 0 0 8 
STO        0               3               0               3               0 0 0 8 0 
LIT        0               9               9               4               0 0 0 8 0 9 
STO        0               4               9               5               0 0 0 8 9 
LOD        0               3               8               6               0 0 0 8 9 8 
LOD        0               4               9               7               0 0 0 8 9 8 9 
OPR        0               12              0               8               0 0 0 8 9 0 

Useful links

Step-by-step execution for PL/0 machine

PL/0 machine functions description

Reference code

Reference code 2