SimpleLang is a subset of assembler languages implemented in virtual machine

In SimpleLang we have only 4 General-Purpose registers r1, r2, r3, r4. One accumulator register A and 4 conditional registers EQ, GT, LT, NE

In SimpleLang only that operations is allowed and implemented:

1. MOV (r|a), (r|a) - store in first operand value from second operand
2. MOV (r|a), @r - store in first operand value by address in second operand
3. ADD A, r - add value from second operand to accumulator
4. DIV A, r - divide value from accumulator by value in second operand (Note: Only integer division is allowe and implemented)
5. SUB A, r - substract accumulator by value of second operand
6. MUL A, r - multiply accumulator by value of second operand
7. LABEL lbl - make that lbl points to that line of code
8. JMP lbl - jump to line that lbl points
9. CMP A, r - compare value of accumulator with second operand and set specific registers
10. JMP_EQ, JMP_LT, JMP_GT, JMP_NE - conditional jumps
11. AND, OR, XOR, NOT - bit operations
12. PRINT (@|)(A|r|num) - print value of register or memory by reg.pointer to stdout
13. INPUT (@|)(A|r) - read ONE NUMBER from stdin and write to register or to memory point
14. CALL lbl - call subroutine under label lbl
15. RET - return from subroutine (Only one subroutine can be called at the monent)

Operation bytecode:

| 2 byte  | 1 byte | 4 byte | 1 byte | 4 byte |
| op_code | arg_ty | op_arg | arg_ty | op_arg |

one operation will be encoded to (2+1+4+1+4) = 12 byte

if operation doesn't have any of arguments pad_sym will be used and arg_type will be set as pad_symbol!

1 byte before every argument is placeholder for argument type (e.g. reference, register or in-place value)

4 byte arguments size needed for in-place values In-place values is a 32-bit integers only!

Every bytecode file have one metadata section before real code

|    2 byte    | 4 byte |
|magical number|   crc  |

CRC sum is used for code invalidation.

Calculate N-th fibonacci number

LABEL MAIN
    INPUT r1
    CALL FIBONACCI
    PRINT r2
    END

LABEL FIBONACCI
    ; Prepare fibonacci
    MOV r2, 0
    MOV r3, 1

    LABEL FIBONACCI_LOOP
        ; Calculate n fibonacci number
        ; Store result at r2

        MOV A, r2
        ADD A, r3

        MOV r2, r3
        MOV r3, A

        SUB r1, 1

        ; Loop while r1 != 0
        CMP r1, 0
        JMP_GT FIBONACCI_LOOP

    RET