bitwise.cpp

Thinking in C++ 2nd edition source code which are all the cores of the book Thinking in C++ second e

//: C03:Bitwise.cpp
// From Thinking in C++, 2nd Edition
// at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// Demonstration of bit manipulation
#include <iostream>
using namespace std;

// A macro to print a new-line (saves typing):
#define NL cout << endl
// Notice the trailing ';' is omitted -- this forces the
// programmer to use it and maintain consistent syntax
// This function takes a single byte and displays it
// bit-by-bit.  The (1 << i) produces a one in each
// successive bit position; in binary: 00000001, 00000010, etc.
// If this bit bitwise ANDed with val is nonzero, it means
// there was a one in that position in val.
void print_binary(const unsigned char val) {
  for(int i = 7; i >= 0; i--)
    if(val & (1 << i))
      cout << "1";
    else
      cout << "0";
}
// Generally, you don't want signs when you are working with
// bytes, so you use an unsigned char.
int main() {
  // An int must be used instead of a char here because the
  // "cin >>" statement will otherwise treate the first digit
  // As a character.  By assigning getval to a and b, the value
  // is converted to a single byte (by truncating it)
  unsigned int getval;
  unsigned char a,b;
  cout << "enter a number between 0 and 255: ";
  cin >> getval; a = getval;
  cout << "a in binary: "; print_binary(a); cout << endl;
  cout << "enter another number between 0 and 255: ";
  cin >> getval; b = getval;
  cout << "b in binary: "; print_binary(b); NL;
  cout << "a | b = "; print_binary(a | b); NL;
  cout << "a & b = "; print_binary(a & b); NL;
  cout << "a ^ b = "; print_binary(a ^ b); NL;
  cout << "~a = "; print_binary(~a); NL;
  cout << "~b = "; print_binary(~b); NL;
  unsigned char c = 0x5A; // Interesting bit pattern
  cout << "c in binary: "; print_binary(c); NL;
  a |= c;
  cout << "a |= c; a = "; print_binary(a); NL;
  b &= c;
  cout << "b &= c; b = "; print_binary(b); NL;
  b ^= a;
  cout << "b ^= a; b = "; print_binary(b); NL;
} ///:~