Help in outputing different file names in a loop

I got this program here which is suppose to output a .ppm file. How can i modify the Filename to get an output of out1.pmm, out2.pmm, out3.pmm .. so on and so forth for a while loop?

Code:

---

unsigned char Filename = "out1.ppm";

while (i < 100)
{

FILE *stream;

stream = fopen(Filename, "wb" );                    // Open the file for write

//rest of the program;
//..
//..

}

---

Code:

---

#include <sstream>
// ...

std::stringstream ss;

while (i < 100)
{
  ss << "out" << i << ".ppm";
  FILE *stream;

  stream = fopen(ss.str().c_str(), "wb" );  // Open the file for write
  ss.str("");                                // clear the stringstream
//rest of the program;
//..
//..

}

---

if this is C++ you probably need to use fstream instead of FILE*

If this is C - you should ask on the proper forum

There's no such need. Iostream laid the last straw on my camel a long time ago. I use stdio.h all the time.