Question

// get user's input
int ch = getch();

switch (ch)
    {
        //input a number
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
            {

            int i = atoi(ch);

            g.board[g.y][g.x] = i;

            }
}

In the code I was given to add on to, ch was declared as an int. However, the function getch saves input as a string, correct? How can I convert the string ch into an int so I can work with it? I tried to use the atoi() function, but I keep getting these error messages.

sudoku.c: In function 'main':
sudoku.c:247:17: error: passing argument 1 of 'atoi' makes pointer from integer without a cast [-Werror]
/usr/include/stdlib.h:148:12: note: expected 'const char *' but argument is of type 'int'
sudoku.c:252:17: error: expected ';' before 'g'
sudoku.c:244:21: error: unused variable 'y' [-Werror=unused-variable]
cc1: all warnings being treated as errors

Answer 1

the function getch saves input as a string, correct?

No, getch reads a character and returns an int (you did correctly define ch as int). The easiest way to convert it to a real integer is to subtract '0'. So after validating getch, you can replace most of your code with:

if (isdigit(ch))
    g.board[g.y][g.x] = ch - '0';