Question

I writing a code for a clock and I’m creating a function to display the time which is stored in an array time[]

char time[]="23:59:45         ";
char display_time(char *t[], char *, char *, char *);

void main(void)             
{
            display_time(&time, &hr, &min, &sec);
            GLCD_GoTo(5,3);
            GLCD_WriteString(time, Font_System7x8);
}

and this is my function

char display_time(char *t[], char *h, char *m, char *s)
{

                *t[0]=*h/10+48;
                *t[1]=*h%10+48;
                *t[3]=*m/10+48;
                *t[4]=*m%10+48;
                *t[6]=*s/10+48;
                *t[7]=*s%10+48;


}

Everything compiles fine but my time isn’t getting update and only the initialized value is being displayed.

Answer 1

• please compile with warnings (gcc -Wall -Wextra)
• display_time should return void
• main should return int and take either (int, char*[]) or (), but NOT (void)
• you can improve the lisibility by passing values (instead of pointers)
• use '0' instead of 48, again for lisibility
• you did not initialize hr. min and sec in your code.
• you should test if h is between 0 and 24 etc.
• you should test for NULL pointer
• display_time doesn’t “display time”, write a better name for the function and you’re done 🙂

.

void display_time(char t[], int h, int m, int s) {
    t[0] = h / 10 + '0';
    t[1] = h % 10 + '0';
    t[3] = m / 10 + '0';
    t[4] = m % 10 + '0';
    t[6] = s / 10 + '0';
    t[7] = s % 10 + '0';
}

int main(int, char*[]) {
    char time[] = "23:59:45";
    int hr = 3, min = 9, sec = 42;
    display_time(time, hr, min, sec);
    GLCD_GoTo(5,3);
    GLCD_WriteString(time, Font_System7x8);
    return 0;
}