ビットシフト

明解Ｃ言語 入門編 > 7. 基本型 >

ビットシフト

C

#include <stdio.h>
int count_bits(unsigned x)

{

    int count = 0;

    while (x)

    {

        if (x & 1u) count++;

        x >>= 1;

    }

    return count;

}
int int_bits(void)

{

    return count_bits(~0u);

}
void print_bits(unsigned x)

{

    int i;

    for (i = int_bits() - 1; i >= 0; i--)

        putchar(((x >> i) & 1u) ? '1' : '0');
    putchar('\n');

}
int main(int argc, char* argv[])

{

    unsigned na = 12345;
    printf("A       = ");  print_bits(na);

    printf("A >> 1  = ");  print_bits(na >> 1);

    printf("A >> 2  = ");  print_bits(na >> 2);

    printf("A >> 3  = ");  print_bits(na >> 3);

    printf("A >> 4  = ");  print_bits(na >> 4);

    putchar('\n');
    printf("A       = ");  print_bits(na);

    printf("A << 1  = ");  print_bits(na << 1);

    printf("A << 2  = ");  print_bits(na << 2);

    printf("A << 3  = ");  print_bits(na << 3);

    printf("A << 4  = ");  print_bits(na << 4);
    return 0;

}

実行結果

R:\>lesson057\project1.exe

A       = 00000000000000000011000000111001

A >> 1  = 00000000000000000001100000011100

A >> 2  = 00000000000000000000110000001110

A >> 3  = 00000000000000000000011000000111

A >> 4  = 00000000000000000000001100000011
A       = 00000000000000000011000000111001

A << 1  = 00000000000000000110000001110010

A << 2  = 00000000000000001100000011100100

A << 3  = 00000000000000011000000111001000

A << 4  = 00000000000000110000001110010000