Pointer code explaination

shanex88 (9)
Hi all, I have the following code using pointer to remove duplicate letter from a user specified key and fill up the empty space with alphabets.
Eg.

key is: testing

the code will remove duplicate alphabet so key will become "tesing"
after that the code will fill the key to make it 26 characters using alphabet without any duplicate.

Eg. "tesingabcdfhjklmopqruvwxyz"

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bool prepareKey(char *key)
{		
	char *pKey1 = key;
	char *pKey2;
	char *pKey3;
	char *pAlpha;

	// if key argument is empty
	if (*pKey1 == '\0')
		return false;

	while (*pKey1 != '\0')
	{
		// contains non alphabetic character
		if (!isalpha(*pKey1))
			return false;

		// convert to lower case
		*pKey1 = tolower(*pKey1);

		// increment to next location
		pKey1++;
	}

	// remove duplicates
	pKey1 = key;

	while (*pKey1 != '\0')
	{
		pKey2 = key;
		
		while (pKey2 != pKey1)
		{
			// duplicate letter found
			if (*pKey2 == *pKey1)
				break;
			
			pKey2++;
			
		}

		if (pKey2 != pKey1)
		{
			pKey2 = pKey1;
			
			while (*pKey2 != '\0')
			{
				pKey3 = pKey2++;
				
				*pKey3 = *pKey2;
				
			}
		}
		else
		{
			pKey1++;
		}
	}

	// fill in the rest of the alphabet
	pAlpha = alphabet;
	
	while (*pAlpha != '\0')
	{
		pKey1 = key;

		while (*pKey1 != '\0')
		{
			if (*pKey1 == *pAlpha)
				break;

			pKey1++;
		}

		if (*pKey1 == '\0')
		{
			*pKey1 = *pAlpha;
			pKey1++;
			*pKey1 = '\0';
		}

		pAlpha++;
	}

	return true;
}

Can anyone give me a walkthrough of how the code do it? Thanks
shanex88 (9)
help please anyone?
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