Lower case to upper case – An interesting fact

// C# program to convert a string to uppercase
using System;

class GFG
{
// Converts a string to uppercase
static String to_upper(char []In)
{
for (int i = 0; i < In.Length; i++) { if ('a' <= In[i] & In[i] <= 'z') { In[i] = (char) (In[i] - 'a' + 'A'); } } return String.Join("", In); } // Driver code public static void Main() { String str = "geeksforgeeks"; Console.WriteLine(to_upper(str.ToCharArray())); } } // This code is contributed by 29AjayKumar [tabbyending] Output :

GEEKSFORGEEKS

A more interesting solution, on the other hand, would be:

Output :

GEEKSFORGEEKS

Explanation: The ASCII table is constructed in such way that the binary representation of lowercase letters is almost identical of binary representation of uppercase letters. The only difference is the sixth bit, setted only for lowercase letters. What that elegant function does is unset the bit of index 5 of in[i], consequently, making that character lowercase.

Disadvantages: That strategy works only for alphabetical characters. If the input contains numbers or punctuations, we’ll have to use the naive way.

Example: Character ‘A’ is integer 65 = (0100 0001)2, while character ‘a’ is integer = 97 = (0110 0001)₂. (Note that 97 – 65 = 32. Can you guess why?)

Exercises:

1. Write a function to make all letters of a string lowercase. Example: GeeksForGeeks turns geeksforgeeks.
2. Write a function that change the case of a string. Example: GeeksForGeeks turns gEEKSfORgEEKS.

This article is contributed by Igor Carpanese. If you like GeeksforGeeks and would like to contribute, you can also write an article and mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above