Changing an array value from a function in C

Question

The program crashes right in the instruction mentioned in the source code (I didn't write all the code because it's too long)

int main()
{
char screen[24][80];

//......every thing is well until this instruction

backgrounds(5,screen);

//......the program doesn't execute the rest of the code

}
//______________________________________________________

//this is a header file

void backgrounds(int choice,char **screen)
{   
    if(choice==5)
    {
        screen[18][18]='-';
        screen[18][19]='-';
        screen[18][20]='-';
    }
}

Answer 1

A char [24][80] cannot be converted to a char **.

When passed to a function, an array decays into a pointer to its first element. This is simple for a 1 dimensional array, but less so for higher dimensions.

In this case, a char [24][80] is an array of char [80]. So passing a variable of this type to a function yields a char (*)[80].

Change your function definition to either this:

void backgrounds(int choice,char (*screen)[80])

Or this:

void backgrounds(int choice,char screen[24][80])

Or you can use a variable length array for maximum flexibility:

void backgrounds(int choice, int x, int y, char screen[x][y])