C Program for LowerCase to UpperCase and vice-versa

Here is the program to convert a string to uppercase in C language,

Example

 Live Demo

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

int main() {
   char s[100];
   int i;
   printf("\nEnter a string : ");
   gets(s);

   for (i = 0; s[i]!='\0'; i++) {
      if(s[i] >= 'a' && s[i] <= 'z') {
         s[i] = s[i] - 32;
      }
   }
   printf("\nString in Upper Case = %s", s);
   return 0;
}

Output

Here is the output

Enter a string : hello world!
String in Upper Case = HELLO WORLD!

In the above program, the actual code of conversion of string to upper case is present in main() function. An array of char type s[100] is declared which will store the entered string by the user.

Then, for loop is used to convert the string into upper case string and if block is used to check that if characters are in lower case then, convert them in upper case by subtracting 32 from their ASCII value.

for (i = 0; s[i]!='\0'; i++) {

   if(s[i] >= 'a' && s[i] <= 'z') {
      s[i] = s[i] -32;
   }
}

Here is the program to convert a string to lowercase in C language,

Example

 Live Demo

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

int main() {
   char s[100];
   int i;

   printf("\nEnter a string : ");
   gets(s);

   for (i = 0; s[i]!='\0'; i++) {
      if(s[i] >= 'A' && s[i] <= 'Z') {
         s[i] = s[i] + 32;
      }
   }

   printf("\nString in Lower Case = %s", s);
   return 0;
}

Output

Here is the output

Enter a string : HELLOWORLD
String in Lower Case = helloworld

In the above program, the actual code of conversion of string to lowercase is present in main()function. An array of char type s[100] is declared which will store the entered string by the user.

Then for loop is used to convert the string into lower case string and if block is used to checkthat if characters are in uppercase then, convert them in lowercase by adding 32 to their ASCII value.

for (i = 0; s[i]!='\0'; i++) {
   if(s[i] >= 'A' && s[i] <= 'Z') {
      s[i] = s[i] + 32;
   }
}