C语言标准库没有整数转二进制字符串函数，随手写一个：

#include "stdio.h"

#include

#include

static const char* LIST[16] = {

"0000", "0001", "0010","0011", "0100", "0101", "0110","0111",

"1000", "1001", "1010","1011", "1100", "1101", "1110","1111"

};

const char* getBinaryStringByIndex(const int index){

if(index<0 || index>15){

return NULL;

}

return LIST[index];

}

void printBinaryNumber(const int num, char* out){

int group = sizeof(num) * 8 / 4;

int i;

for(i=0; i

int index = (num >> (group-i-1)*4) & 0x0f;

const char* groupResult = getBinaryStringByIndex(index);

strcpy(out+i*4, groupResult);

}

}

int main(){

int a = 1997;

int len = sizeof(a)*8;

char* result = (char*) calloc(len+1, 1);

if(!result){

printf("alloc memory failed");

return -1;

}

printBinaryNumber(1997, result);

printf("result: %s", result);

free(result);

return 0;

}

输出如下：