CSC231 Powers of 2 in C++

--D. Thiebaut 13:43, 8 October 2010 (UTC)

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This exercise is a companion of the same exercise dealing with a Python implementation of the program.

Exercise

• Below is a C++ program, and its complete output

Question 1

Explain this output!

Question 2

Remove the word unsigned from the program. This changes the integer variable from an unsigned variable to a signed one.

Change the %u printing format command by %d to indicate that you want to print the contents of a signed variable.

Predict the output of the program.

The C++ Program

// loopForever.cpp
// D. Thiebaut
// To compile and run:
// 
//   g++ -o loopForever loopForever.cpp
//   ./loopForever
//
#include <stdio.h>

int main() {
  unsigned int x = 1;

  while ( x != 0 ) {
    printf ( "%u\n", x );
    x = x * 2;
  }

  // printf( "final x = %u\n\n", x );
  return 0;
}

The Output

g++  -o  mulby2  mulby2.cpp

./mulby2 

1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072
262144
524288
1048576
2097152
4194304
8388608
16777216
33554432
67108864
134217728
268435456
536870912
1073741824
2147483648