main.c

#include <c64.h>
#include <stdio.h>

unsigned byte* const SCREEN = (char*)$0400;

void main() {
    fillscreen(SCREEN, $20);
    charset();
}

void charset() {
    unsigned byte i = 0;
    unsigned byte max = 32 + 32 + 32 + 2;
    do {
        unsigned byte column = (i % 32) + 4;
        unsigned byte row = (i / 32) + 4;
        unsigned byte *pointer = SCREEN + (row * 40) + column;
        *pointer = i;
        //printf("row %u, col %u - %p\n", row, column, pointer);
        i++;
    } while (i != max);
}

void fillscreen(char* screen, char fill) {
    for( char* cursor = screen; cursor < screen+1000; cursor++) {
        *cursor = fill;
    }
}