C / C ++ language codes Integer binary string

No non-standard library functions, their own hand write a conversion function:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static char* CONST_4BITS_LIST[16] = {
    "0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111",
    "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"
};

void convert(char c, char* out){
    strcpy(out, CONST_4BITS_LIST[c >> 4 & 0x0f]);
    strcpy(out+4, CONST_4BITS_LIST[c & 0x0f]);
}

int main() {
    char buf[9] = {0};
    long long int a = 0x0123456789abcdef;
    char* p = (char*)&a;

    for(int i=0; i<sizeof(a); i++){
        convert(*(p+i), buf);
        printf("%s\n", buf);
    }

    return 0;
}

 

 

 Again a C ++ is:

#include <cstdio>
#include <cstdlib>
#include <cstring>

static const char* CONST_4BITS_LIST[16] = {
    "0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111",
    "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"
};

void convert(char c, char* out){
    strcpy(out, CONST_4BITS_LIST[c >> 4 & 0x0f]);
    strcpy(out+4, CONST_4BITS_LIST[c & 0x0f]);
}

int main() {
    char buf[9] = {0};
    long long int a = 0x0123456789abcdef;
    char* p = (char*)&a;

    for(int i=0; i<sizeof(a); i++){
        convert(*(p+i), buf);
        printf("%s\n", buf);
    }

    return 0;
}