1. ## Number System !!!

I want to do like this:

cin >> hex >> num;
cout << num ;
cout << dec << num;

cin >> oct >> n;
cout << n;

cin >> base(3) >> nnn;
cout << base(19) << nn;

What I have to do? Have you any code ???

2. You can search the board and probably find some reasonable approaches. When I did this I set up a system whereby I could convert any base to base 10 and then from base 10 to any base, but I'm sure there are different approaches.

3. I wrote an example program for this, but I don't have it here at work... I can post it this evening (California time).

The decimal, hex, octal input/output is easy using cout. There is a standard function for getting input in (almost) any base [strtoul() = string-to-long]. There is a non-standard function with the Microsoft compiler to display in (almost) any base... I don't remember what it's named.

4. Hello!

Code:
```#include<iostream.h>
#include<iomanip.h>
#include<stdlib.h>
#include<string.h>

int main()
{
char str[20];
unsigned long int n;

while(cin.getline(str,20))
{
if(str[0]=='0' && str[1]=='x')
{
char s[20];

for(int i=2;i<strlen(str);++i)
s[i-2]=str[i];

n = atol(s);
cout << dec << n << endl;
}
else if(str[0]=='-')
{
return 0;
}
else
{
n = atol(str);
cout << "0x";
cout << hex << n << endl;
}
str[0]=0;
n=0;
}

return 0;
}```
It was working but when the first segment converting hex to dec is not working as it only takes dec form and converts it to oct or hex. any suggestion. ???

5. >>n = atol(s);
That won't work. It only works for base 10. You're gonna have to write your own function to go from hex->decimal.

6. Here's a base converter I just threw together quickly. It can convert between bases 2-36.

7. ## Here's my example.

Have fun!

8. This has a C example, but the strtol() function can be used in C++ too.