C Programming: Replace lowercase characters by uppercase and vice-versa

C String: Exercise-15 with Solution

Write a program in C to read a sentence and replace lowercase characters by uppercase and vice-versa.

Sample Solution:

C Code:

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

void main()
{
  char str[100];
  int ctr, ch, i;

       printf("\n\nReplace lowercase characters by uppercase and vice-versa :\n");
       printf("--------------------------------------------------------------\n");	

	   printf("Input the string : ");
       fgets(str, sizeof str, stdin);  

  i=strlen(str);

  ctr = i; /*shows the number of chars accepted in a sentence*/

  printf("\nThe given sentence is   : %s",str);

  printf("After Case changed the string  is: ");
  for(i=0; i < ctr; i++)
  {
    ch = islower(str[i]) ? toupper(str[i]) : tolower(str[i]);
    putchar(ch);
   }
   printf("\n\n");

} 

Sample Output:

Replace lowercase characters by uppercase and vice-versa :                                                    
--------------------------------------------------------------                                                
Input the string : This Is A Test String                                                                      
                                                                                                              
The given sentence is   : This Is A Test String                                                               
After Case changed the string  is: tHIS iS a tEST sTRING 

Flowchart :

C Programming Code Editor:

Improve this sample solution and post your code through Disqus.

Previous: Write a C program to check whether a given substring is present in the given string.
Next: Write a program in C to find the number of times a given word 'the' appears in the given string.