In depth analysis of C++ function itoa of

The function itoa() is a function that converts an integer type toa c-style string The prototype:
Char * itoa (int data, char*p, int num);
Data is the incoming converted number, is the integer variable (the maximum value of data is 2 to the 31st power minus 1), p is the incoming character pointer, pointing to the first address of the converted string space; Num specifies the string of digits to be converted to (binary, octal, decimal, hexadecimal).
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//TestInheritance. CPP: defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
#include <string>
#include <math.h>
using namespace std;
int myItoa(int data, char* p, int num)
{
 if (p == NULL)
 {
  return -1;
 }
 if (data < 0)
 {
  *p++ = '-';
  data = 0 - data;
 }
 int temp = 0;
 int flag = 0; //Flag bit 0- does not store 1- stores
 if (num == 10)
 {//The decimal system
  for (int i = 0; i < 10; i++)
  {
   temp = static_cast<int>(data / pow(10.0, 9-i));//Pow of I,j, I to the j, temp takes the current highest bit
   if (temp != 0)  //We get rid of the first 0
   {
    flag = 1;//Changes the flag bit to 1 and can be stored
   }
   if (flag != 0)
   {
    *p++ = temp + '0';  //Become character
    data = data % static_cast<int>(pow(10.0, 9-i));
   }
  }
 }
 else if (num == 2)
 {//binary
  for (int i = 0; i < 32; i++)
  {
   temp = static_cast<int>(data / pow(2.0, 31-i)); //Int, Max. (2 ^ 31 -1),
   if (temp != 0)
   {
    flag = 1;
   }
   if (flag != 0)
   {
    *p++ = temp + '0';
    data = data % static_cast<int>(pow(2.0, 31 - i));
   }
  }
 }
 else if (num == 16)
 {//hexadecimal
  for (int i = 0; i < 8; i++)
  {
   temp = static_cast<int>(data / pow(16.0, 7-i));
   if (temp != 0)
   {
    flag = 1;
   }
   if (flag != 0)
   {
    if (temp >= 0 && temp <= 9)
    {
     *p++ = temp + '0';
    }
    else if (temp >= 10 && temp <= 15)
    {
     *p++ = temp - 10 + 'A';
    }
    data = data % static_cast<int>(pow(16.0, 7 - i));
   }
  }
 }
 else if (num == 8)
 {//octal
  for (int i = 0; i < 16; i++)
  {
   temp = static_cast<int>(data / pow(8.0, 15-i));
   if (temp != 0)
   {
    flag = 1;
   }
   if (flag != 0)
   {
    *p++ = temp + '0';
    data = data % static_cast<int>(pow(8.0, 15-i));
   }
  }
 }
}
int _tmain(int argc, _TCHAR* argv[])
{ 
 int i = 100;
 char a[32] ={0};
 char b[32] ={0};
 char c[32] ={0};
 char d[32] ={0};
 cout << i << " the octal Represented as a : ";
 myItoa(i, a, 8);
 cout << a << endl;
 cout << i << " the The decimal system Represented as a : ";
 myItoa(i, b, 10);
 cout << b << endl;
 cout << i << " the binary Represented as a : ";
 myItoa(i, c, 2);
 cout << c << endl;
 cout << i << " the hexadecimal Represented as a : ";
 myItoa(i, d, 16);
 cout << d << endl;
 return 0;
}