conversion issues

[ui uiho]

i am making a battle ship program for my class, the teacher wants me to use a 2d array to replicate a one player battleship game. i have having trouble converting a letter into a value. here is my code

//
//  main.cpp
//  battleship
//
//  Created by Home on 3/30/12.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

#include <iostream>
#include <fstream>
#include <exception>
#include <ctype.h> 
void printinfo();
void printfield(char array[6][6]); 
void printlane(int i, char array[6][6]); 
bool check(int i, int j, char map[6][6]); 
int charcovert(char c); 

int main(){
    std::string s;
    int row, collumn = 7, ship = 0; 
    bool sunk = false; 
    std::ifstream ship_location;
    ship_location.exceptions(std::ifstream::failbit | std::ifstream::badbit);
    // [row] [collumn] 
    char field[6][6], player[6][6] = {}; 
    //open file
    try{
        ship_location.open("/Users/home/Desktop/battleship/battleship/ship.txt");
    }
    //catch error
    catch (std::ofstream::failure &e){
        std::cout << "An error has occured";
        return 1; 
    }
    //upload array
        for(int j = 0; j < 6; j++){
    for(int i = 0; i < 6; i++){
        ship_location >> field[j][i]; 
    }
}
    ship_location.close(); 
    printinfo();
    
    while(!sunk){
        printfield(player); 
        std::cout << "enter in your location!(q to exit)";
        std::cin >> s;
        s[0] = charcovert(s[0]);
        collumn = atoi(&s[0]);
        while(collumn == 7){
            std::cout << "Entered invalid number please enter new row: ";
            std::cin >> s[0]; 
            collumn = atoi(&s[0]);
        }
        row = atoi(&s[1]); 
        std::cout << '\n' << row << " " << collumn;
        return 0;//debugging
        if(check(row, collumn, field)){
            player[--row][--collumn] = 'H';
            ship++; 
        }
        else {
            player[row][collumn] = 'M'; 
        }
        if(row == 0) sunk = true;
        if(ship == 3) sunk = true; 
    }
    
    return 0;
}

int charcovert(char c){
    tolower(c); 
    if(c == 'a') return 1;
    if(c == 'b') return 2;
    if(c == 'c') return 3; 
    if(c == 'd') return 4;
    if(c == 'e') return 5;
    if(c == 'f') return 6;
    if(c == 'q') return 0; 
    else return 7; 
}

bool check(int i, int j, char field[6][6]){
    if(field[i][j] == 'S') return true;
    else return false; 
}

void printfield(char array[6][6]){
    std::cout << "\n  A B C D E F\n";
    for(int i = 0; i < 6; i++){
        std::cout << i + 1 << " "; printlane(i, array); 
        std::cout << '\n'; 
    }
}

void printlane(int i, char array[6][6]){
    for(int j = 0; j < 6; j++){
        std::cout << array[i][j] << " ";
    }
}

void printinfo(){
    std::cout << "********************";
    std::cout << "\n*                  *";
    std::cout << "\n*     BATTLESUB!   *";
    std::cout << "\n*     by me!       *"; 
    std::cout << "\n*                  *";
    std::cout << "\n********************"; 
}

i have tried a few methods of coverting and this is the only one i get a real number but still returns a 0 value for some reason. thanks in advanced.