# Bit Manipulation Application Small to Capital Letter

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One of several applications of bit manipulation is converting a letter from small to capital or vice versa by choosing a mask and a proper bit operation. For example, the a letter has this binary representation `01(1)00001` while its capital counterpart has `01(0)00001`. They differ solely in the bit in parenthesis. In this case, converting the a letter from small to capital is basically setting the bit in parenthesis to one. To do so, we do the following:

``````/****************************************
convert small letter to captial letter.
========================================
a: 01100001
mask: 11011111  <-- (0xDF)  11(0)11111
:---------
a&mask: 01000001  <-- A letter
*****************************************/``````

The code for converting a letter to A letter is:

``````#include <cstdio>

int main()
{
char op1 = 'a';  // "a" letter (i.e. small case)
int mask = 0xDF; // choosing a proper mask

printf("a (AND) mask = A\n");
printf("%c   &   0xDF = %c\n", op1, op1 & mask);

return 0;
}``````
``````a (AND) mask = A
a   &   0xDF = A
``````