Write the UPPER function that converts all letters in a string to uppercase.

Difficulty level
Video recording
This exercise is mostly suitable for students 
#include <stdio.h>
#include <conio.h>

void UPPER(char str[])
{
	int i = 0;
	for (; str[i]; i++)
		if (str[i] >= 'a' && str[i] <= 'z')
			str[i] = str[i] - 'a' + 'A';
}

void main()
{
	char str[100];
	printf("Enter a string: ");
	gets(str);
	UPPER(str);
	puts(str);

	getch();
}
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