basic_vm.c

#include <stdio.h>
#include <stdbool.h>

bool running = true;   //check running status
int ip = 0;                     //Instuction Pointer
int sp = -1;                    //Stack Pointer

int stack[256];             //VM's Ram

typedef enum {
        PSH,
        ADD,
        POP,
        HLT
}   InstructionSet;             //supported opcodes for VM

const int program[] = {
    PSH, 5,
    PSH, 6,
    ADD,
    POP,
    HLT
};                              //code to be executed inside VM

int fetch() {
    return program[ip];
}

void eval(int instr) {              //VM implementation
    switch(instr) {
        case HLT: {
            running=false;
            printf("Done\n");
            break;
        }
        case PSH: {
            sp++;
            stack[sp] = program[++ip];
            break;
        }
        case POP: {
            int val_popped = stack[sp--];
            printf("popped %d \n",val_popped);
            break;
        }
        case ADD: {
            int a=stack[sp--];
            int b=stack[sp--];
            int result = b+a;
            sp++;
            stack[sp]=result;
            break;
        }
    }
}

int main() {
    while(running) {
        eval(fetch());
        ip++;
    }
}