C program to convert uppercase string to lowercase string

Program:

#include<stdio.h>
#include<string.h>

int main()
{
    char str[20];
    int i;

    printf("Enter string : ");
    gets(str);
 
    for(i=0;i<=strlen(str);i++)
    {
    if(str[i]>=65&&str[i]<=90)
    str[i]=str[i]+32;
    }
    printf("String in lowercase : %s",str);
    return 0;
}

Output :