求助：自学中题看不懂，看了书上的答案还是没看懂题，怎么办啊？？ - C语言论坛

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求助：自学中题看不懂，看了书上的答案还是没看懂题，怎么办啊？？

求解释这道题到底想做什么？

书中的编程练习题：

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书中答案：

程序代码：

#include <limits.h>

void set_bit(char bit_array[], unsigned bit_number);
void clear_bit(char bit_array[], unsigned bit_number);
void assign_bit(char bit_array[], unsigned bit_number, int value);
int test_bit(char bit_array[], unsigned bit_number);

unsigned character_offset(unsigned bit_number);
unsigned bit_offset(unsigned bit_number);

void
set_bit(char bit_array[], unsigned bit_number)
{
    bit_array[character_offset(bit_number)] |= 
        1 << bit_offset(bit_number);
}

void
clear_bit(char bit_array[], unsigned bit_number)
{
    bit_array[character_offset(bit_number)] &=
        ~(1 << bit_offset(bit_number));
}

void
assign_bit(char bit_array[], unsigned bit_number, int value)
{
    if (value != 0)
        set_bit(bit_array, bit_number);
    else
        clear_bit(bit_array, bit_number);
}

int
test_bit(char bit_array[], unsigned bit_number)
{
    return (
        bit_array[character_offset(bit_number)]
        & 1 << bit_offset(bit_number)
        ) != 0;
}

unsigned
character_offset(unsigned bit_number)
{
    return bit_number / CHAR_BIT;
}

unsigned
bit_offset(unsigned bit_number)
{
    return bit_number % CHAR_BIT;
}