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The strupr() is string function defined in the string.h header file, which is used to convert all the characters in a String to upper case letters.

Signature of strupr() function

char * strupr(char *str);

• str - is a string passed to this method, whose lower case characters needs to be converted to upper case.
• This method changes the character of string passed to it to upper case and returns a char[] array pointer, pointing to this string whose characters are converted to upper case.

Note

The function strupr() when called on any char[] array, containing a string value, returns its contents as an upper case string.

• Example of strupr() function




/* Program to convert a String to upper case letters */


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

int main()
{
char str1[] = "new zealand";
printf("Original String value : %s", str1);
printf("\n");
strupr(str1);
printf("String's upper case value : %s ", str1);

return 0;
}





Output




Priginal string value : new zealand
String's upper case value : NEW ZEALAND


A char[] array was initialized with a string value new zealand. When this string was passed to strupr() function, it changed all the characters in string to upper case letters.




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• Changing the characters in a string to upper case without strupr()


Let's create a program which converts the characters in a string to upper case letters without using strupr() function.




/* Program to convert a String to upper case letters withut strupr() function */


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

int main()
{
char str[] = "new zealand";
printf("Original String is : %s", str);


/* starting index in a char{} array is always zero, 0 */
int i=0;


while(str[i]!='\0')
{
int asc = str[i];
	
	/* When ASCII value of a space is found */
	if(asc==32)
	{
		/* we don't do anything */
	}


	/* When alphabetic characters are found */
	if(asc>=97 && asc<=122)
	{
		asc = asc - 32;
		str[i] = asc;

	}
	
	/* incrementing the index to point to next char value in string */
	i++;
}	


printf("\nString's upper case value : %s", str);

return 0;
}





Output is :




Original String is : new zealand
String's upper case value : NEW ZEALAND


In the code above, we have changed the cases of characters in a char[] array(which contains a string) to upper case, without using the strupr() function. To achieve this, we have used the index of each character in a char array to read its ASCII value. When an ASCII value of a character is found to be between 97 and 122, we have subtracted 32 from it, which results in the ASCII value of its upper case equivalent.






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