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Simple, Simple Questions

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After finishing "An Absolute Beginner''s Guide to C" I picked up "The C Programming Language". I have gone through the first few chapters and I understand most of it, but two things are confusing me, and if you could answer them it would be much appreciated. First off, can someone explain EOF a little better. All I caught was that it was an integer defined in ?(stdio.h)?, I forget, but I don''t see what the purpose of it is, and whether it can make the first few programs not an endless loop. And I have no idea what bitwise operators are doing. If anyone could explain the bits thing or direct me somewhere where I could it would be helpful. Thanks.

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EOF = End of File. For example:
      
while ( x != EOF )
{
file.get(x); // read in a new character

}



It's just a way of checking to see if you've hit the end of the file.

Bitwise operators are operators the work on individual bits. For example the number 7 in binary is 0000 0111. If we do a bitwise AND with 6(0000 0110) we do an AND on all the individual bits.


0000 0111
0000 0110
-----------
0000 0110

So 7 & 6 = 6

The are most often used as flags. For example:
  

#define FLAG_1 1

#define FLAG_2 2

#define FLAG_3 4

#define FLAG_4 8


//Set a test to both FLAG_1 and FLAG_4

int testFlag = FLAG_1 | FLAG_4;
// 0000 0001 OR

// 0001 0000

//------------

// 0001 0001

// testFlag will be 0001 0001


// Test to see if FLAG_4 has been set

if ( testFlag & FLAG_ 4 )
{
//0001 0001 AND


// 0001 0000

// ------------

// 0001 0000

// Thus the test condition is true therefore FLAG_4 has been set


}



Hope this helps a little. Try going to google and typing in "Bitwise operators in C++ tutorial" I'm sure that you will get lots of hits with better examples


-------------
Andrew



Edited by - acraig on August 25, 2001 2:18:51 PM

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