Code for UPPER and REVERSE

[Unregistered]

A user inputs a string of lower case alphabetic letters, and i need to output the string in reverse order in upper case, ie. "abcd" becomes DCBA. However, im not allowed to use any library functions. Can anyone tell me what code i would need to do these two (upper and reverse) functions manually?

Thanks

[Deckard]

Printing the string in reverse is easy. Simply place a pointer on the last character of your string and move backwards. You will want to know the length of the string in advance, so you don't fall of the end (or in this case, the front) of the string.

You can convert lower case to upper with the bitwise AND operator:

char c = 'a';

c &= 223;  /* The value held by c is now 'A' */

[Unregistered]

thanks, but can you elaborate on the &= 223 part please? Im unsure as to what that number means

[Deckard]

Certainly. In the ASCII character set, the only difference between any lower case letter and its capital counterpart is a single bit (the bit representing the value 32). For example:

• a = 01100001
  A = 01000001
  
  j = 01101010
  J = 01001010

You can use the bitwise AND operator to flip a single bit:

• 01100001 (a)
  11011111 (223)
  --------- (&)
  01000001 (A)

There was a good discussion about bitwise operators in general in this thread.

[WayTooHigh]

// ** this loop gets the length of a_string
do
{
	an_int++; // ** when declaring this make it zero
}
while(a_string[an_int-1] != '\0');



// ** this loop reverses and capitalizes a_string into a_new_string
for(another_int = 0; an_int-1 > 0; an_int--)
{
	a_new_string[another_int] = a_string[an_int-2]-32;
	another_int++;
}