#include <stdio.h>

int func(){

	static int count = 1;

	return ++count;

}

int main()

{

	int answer = 0;

	answer = func() - func() * func();

	printf("%d\n", answer);

	return 0;

}

#include <stdio.h>

//反转bit位

unsigned int reverse_bits(unsigned int value)

{

	unsigned int result = 0;

	unsigned int tmp = 1;

	//计算unsigned int位数

	int len = sizeof(unsigned int) * 8;

	int idx;

	//每次向右位偏移一位

	for(idx = 0; idx < len; idx++){

		//判断bit值，如果是1

		if(((value >> idx)) & 1){

			//则将tmp中对应的另一端的位置为1

			tmp = 1 << (len - idx - 1);

			//tmp和result取或运算置位1

			result |= tmp;

		}

	}

	return result;

}

//将value二进制形式打印出来

void print_bits(unsigned int value)

{

	int len = sizeof(unsigned int) * 8;

	int idx;

	int bit;

	for(idx = 1; idx <= len; idx++){

		//从左往右，通过位偏移后，和1取与运算，打印bit位的值

		bit = 1 & (value >> (len - idx));

		printf("%d", bit);

		//四位一空，方便阅读

		if(idx % 4 == 0){

			printf(" ");

		}

	}

	printf("\n");

}

int main()

{

	unsigned int input = 25;

	unsigned int result;

	printf("%d\n", input);

	print_bits(input);

	result = reverse_bits(input);

	printf("%u\n", result);

	print_bits(result);

	return 0;

}

25

0000 0000 0000 0000 0000 0000 0001 1001

2550136832

1001 1000 0000 0000 0000 0000 0000 0000

#include <stdio.h>

int store_bit_field(int original_value, int value_to_store, unsigned starting_bit, unsigned ending_bit)

{

	int mask = 0;

	int tmp  = 0;

	//制作对应的起始位置掩码

	for(int idx = starting_bit; idx >= ending_bit; idx--){

		tmp = 1 << idx;

		mask |= tmp;

	}

	//通过掩码将original_value 对应的范围内置0

	original_value &= ~mask;

	//将value_to_store对齐起始和结束位置

	value_to_store  <<= ending_bit;

	//value_to_store中将超出范围的部分置0

	value_to_store &= mask;

	//将值和original_value取或保存值

	original_value |= value_to_store;

	return original_value;

}

int main()

{

	int result;

	result = store_bit_field(0xffff, 0x123, 13, 9);

	printf("0x%0x\n", result);

	return 0;

}

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