Question

I am trying to learn assembly my self, and I have been reading different websites first to know the meaning of some registers, if-the, etc, and saw examples on how to use them.

However I don’t find it easy to understand. This program finds certain letters and counts them in a board using a bidimensional array. I want to replace the part of the functions void print_results(), and void count() with assembly code since this is very easy in regular C code.

I am not sure how to start so I am more interested on just a good start, specially on how to pass the variable from void read_board() to the function void count() to count the letters found, after that I think I can be on my own.

I appreciate any help, Thank you.

#include <stdio.h>

FILE *inputFilePtr;
char board[7][7];

void usage() {
    printf("usage: one filename argument.\n");
}

void read_board() {
    int i, j;
    for (i=0; i != 7; i++) {
        for (j=0; j != 7; j++) {
            fscanf(inputFilePtr, "%c", &board[i][j]);
        }
        fscanf(inputFilePtr, "\n");
    }
}

void count() {

     __asm__("\
      ");

}

void print_results() {

}

int main(int argc, char**argv) {
    if (argc != 2) {
        usage();
        return 1;
    }

    inputFilePtr = fopen(argv[1], "r");
    if (inputFilePtr == NULL) {
        printf("Couldn't open file, %s\n", argv[1]);
        return 1;
    }

    read_board();

    count();

    print_results();

    return 0;
}

Answer 1

I am assuming you want the C-equivalent that does your current asm part.

Since you array board is global and your board size is fixed (7×7), you don’t need pass anything to count(). This will do:

void count() {
int i, j, count = 0;
char = 'X'; //Replace with whatever char you want to count 

  for (i=0; i != 7; i++) {
        for (j=0; j != 7; j++) {
          if(board[i][j] == c)
             count++;
       }
   }
}

Then simply call count() from wherever you want.

In case if you want to know how to pass parameters to functions (if the board, i & j are not global like your case):
call count as: count(&board[0][0], int i, int j);

Receive the parameters as: void count(char **board, int i, int j)