C - Bitwise operation - Bit shift in decimal

Let’s try to transform a binary into a decimal with a simple loop.

Let’s see this example of a bit shift into a decimal display:

#include        <stdio.h>

int     main()
{
  int   i;
  int   j;

  i = 0;
  j = 1;
  printf("%d\n", j);
  while (i < 32)
    {
      j = j << 1;
      printf("%d\n", j);
      i++;
    }
  return (0);
}

Let’s compile and execute it:

$ cc main.c && ./a.out

Result:

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
0

I’m seeing some of you saying : “Uh why?”

It’s easy. For this example, D = decimal, B = binary

D 1 = B 1
D 2 = B 10
D 3 = B 11
D 4 = B 100

Some of you start to understand!

Indeed, each bit shift means that we add 1 on the left with only 0 after.
Example in binary:

00000001
00000010
00000100
00001000
00010000
00100000
Etc.
This is equivalent in decimal to:
1
2
4
8
16
32
Etc.