Bitwise (need help not answer)

[MSF1981]

I'm studying bit manipulation. My assignment is to write two functions. 1. convert string to all upper, 2. convert string to all lower. The trick is that I cannot use toupper or tolower. I have to use bit manipulation. I have read many articles and the chapters of various books on bitwise. It's very hard to find real world examples showing bit manipulation in C. Or at least I just don't know how to look for them.

What I know (or think I know)...
I understand that the easiest way to manipulate bits in C is to use hex. I have read and understand the basics of binary and hexadecimal. I understand that the difference between an uppercase character and a lowercase character is the 3rd lower order bit (I think). I understand how to create a mask to turn on and off this bit. But I just don't get how to get a char (getchar?), and manipulate a specific bit of that character using the mask.

Can anyone suggest a tutorial or provide any insight?

[tabstop]

Any tutorial that covers bitwise should be good. Remember, everything stored in the computer is already in bits, so you don't do anything to a character (or whatever) to get it ready.

[King Mir]

To get a character from a string is just str[i], where str is the string, and i is the index.

To manipulate a specific bit use:

chtr |= MASK; /*sets all bits that are set in MASK*/
chtr &= MASK; /* resets bits not set in MASK*/

[sean]

Look in stdio.h - you'll find all the input/output functions.

Specifically, getc will give you a single char, or you could work on a string and access a specific char ( string[0] ), or better yet, get a string and use a loop to perform the operation on every char inside it!

[ganesh bala]

Upper =>Lower

u can use bitwise OR for characters in string .. like char1 =char1 |32

[MSF1981]

You all are awesome! Here is what I have so far... Not working yet but not sure if that's because of other problems in my program...

char* b_returnLowerCase(char originalString[], char lowerString[])
{
	int i;
	int length = strlen(originalString);

	for (i = 0; i < length; ++i)
	{
		lowerString[i] = originalString[i] | MASK;
	}
	lowerString[i] = '\0';
	puts(lowerString);

	return lowerString;
}