C Program to convert a string from lowercase to uppercase

In this C Programming example, we will implement the program to convert a string from lower case to upper case and print the output on the screen.

1. String case Conversion – Lower Case to Upper Case

String Case Conversion is a process to convert each character of a string to either Uppercase or to Lowercase characters.

Example
Enter the string which needs to be converted : happy birthday
The String in Upper Case is = HAPPY BIRTHDAY

Helpful topics to understand this program better are-

• Data Types in C
• Console Input / Output in C
• Functions in C
• For and while loop in C

2. C Program to convert a string from lower case to upper case

Let’s discuss the execution(kind of pseudocode) for the program to convert a string from lower case to upper case in C.

1. Initially, the program will prompt the user to enter the string that needs to be converted.
2. The string is now passed to a function convertLowerToUpper().
3. In the convertLowerToUpper() function, For loop is used to convert the entered string into an uppercase string and if statement is used to check whether the characters are in lower case or not.
4. If the string is in the lower case then convert the string into the upper case by subtracting 32 from their ASCII value.

Let us now implement the above execution of the program to convert string from lower case to upper case.

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

char string[1000];

void convertLowerToUpper() {
  int i;
  for (i = 0; string[i] != '\0'; i++) {
    if (string[i] >= 'a' && string[i] <= 'z') {
      string[i] = string[i] - 32;
    }
  }
}
int main() {
  printf("\nEnter the string : ");
  gets(string);
  convertLowerToUpper();
  printf("\nThe String in Upper Case = %s", string);
  return 0;
}

Note: The above program can also be implemented using a while loop as well.

Output
Enter the string : lower to upper
The String in Upper Case = LOWER TO UPPER

3. Conclusion

In this C Programming example, we have discussed how to convert a string from lower case to upper case using the ASCII values.

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