Changing Cases in a String

ASCII values and it's importance in changing cases in a string.

Common ASCII Codes:

  • A = 65
  • Z = 90
  • a = 97
  • z = 122

The Logic:

To covert from uppercase to lowercase, add 32 to the uppercase character.
To convert from lowercase to uppercase, subtract 32 from the lowercase character.

C Function:

void toUpper(char A[]) {
for (int i = 0; A[i] != '\0'; i++) {
A[i] = A[i] - 32;
}
}
​
void toLower(char A[]) {
​
for (int i = 0; A[i] != '\0'; i++) {
A[i] = A[i] + 32;
}
​
}
​
void toggleCase(char A[]) {
​
for (int i = 0; A[i] != '\0'; i++) {
if (A[i] >= 'A' && A[i] <= 'Z') {
A[i] = A[i] + 32;
} else if (A[i] >= 'a' && A[i] <= 'z') {
A[i] = A[i] - 32;
}
}
​
}
Contributed by Nitin Ranganath