Decimal to Binary conversion with quotient in C - c

Question

I try to create a program which converts Decimal to Binary and back. My problem is when the fraction part becomes too big in binary, my program crashes. I tried many different approaches to this problem and none of them worked...I dont know why it happens so I have no sollution for it.
This program contains only the issue.
Please help me.
example1: 10 10.5 -> Program works fine
example2:10 10.23 -> Program crashes
Above are examples.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
int main(){
int base;
double number;
scanf("%d %lf",&base,&number);
if(base == 10){
//Integer Part
int n = (int)number;
number = number - (double)n;
int i = 0;
char *binaryfirst;
binaryfirst = malloc(sizeof(char*));
while(n != 0){
binaryfirst[i] = (n % 2) + '0';
n /= 2;
i++;
}
binaryfirst[i] = '\0';
strrev(binaryfirst);
//printf("%lf\n%s\n",number,binaryfirst);
//Fractional part
int j = 0;
char *binarysecond;
binarysecond = malloc(sizeof(char*));
//This is The part where I am lost...
for(j = 0; j < 60; j++){ //60 is the maximum length that it can become
number *= 2;
if(number >= 1.0){
binarysecond[j] = '1';
number = number - 1;
}else if(number == 0){
binarysecond[j] = '0';
break;
}else{
binarysecond[j] = '0';
}
printf("%lf; %c\n",number, binarysecond[j]);
}
printf("%d\n",j);
binarysecond[j] = '\0';
//printf("\n%s\n",binarysecond);
//Memory "Let it go"!!!!
/* for(i = 0; i < sizeof(binaryfirst); i++){
free(binaryfirst[i]*2);
}*/
free(binaryfirst);
/* for(j = 0; j < sizeof(binarysecond); j++){
free(binarysecond[j]);
}*/
free(binarysecond);
}
return 0;
}

Answer 1

This:
binaryfirst = malloc(sizeof(char*));
and
binarysecond = malloc(sizeof(char*));
allocates the size of a pointer, but the loop that writes to it makes it clear that it expects to store at most 60 bytes at that location. This makes no sense at all; C does not magically grow the allocation when you write outsite it, instead you get undefined behavior.
If you're unsure about heap memory allocations, and they're not crucial to the problem you're trying to solve, first do it without any. Just use simple arrays:
char binaryfirst64];
char binarysecond[64];