Reverse string in C

main.c

// Program is divided into two smaller parts so you can see how the
// things actually work.

#include <stdio.h>

int strlen(char *s)
{
    int i = 0;
    while (*s++)
        i++;

    return i;
}

char *reverse(char *str)
{
    int front, rear;
    for (front = 0, rear = strlen(str) - 1; front < rear; front++, rear--) {
        char tmp = str[front];
        str[front] = str[rear];
        str[rear] = tmp;
    }

    return str;
}

int main()
{
    char str[] = "JQR";
    printf("%s\n", reverse(str));
    return 0;
}