still problem of organize file

Hi all

on last post I confused on how to organize file of class, ok ,the problem
solved : should include class define head on cpp file.
but this time ,still link error:

strange is I put the implement to .h file directly like this:
*******head file*****
class LinuxTestTerminal : public Terminal{
public:
  void printch(char ch){
      fprintf(stdout,"%c",ch); <--- directly implement here
  }
};

there's no error occur;

but when I wrote the .cpp file,(same name as .h file)
*******head file*****
class LinuxTestTerminal : public Terminal{
public:
  void printch(char ch);
};

*******cpp file******
#include "LinuxTestTerminal.h"
void
LinuxTestTerminal::printch(char ch){
    fprintf(stdout,"%c",ch);
}

error occurs: undefined reference of printch();

What's on earth the problem is?

thank you very much!

                    key9

completed code here : cygwin enviroment

// test.cpp
// use -lstdc++

#include <stdio.h>
#include <unistd.h>
#include <iostream>

#include "LinuxTerminal.h"

using namespace std;

//this printch function is just for test ,direct use this can pass the test
print
/* void printch(char ch){
  fprintf(stdout,"%c",ch);
}
*/

int main(int argc, char *argv[])
{
  char q = 'c';

   printf("print a new line of doing test");

   LinuxTestTerminal* lt = new LinuxTestTerminal();
   lt->printch(q);

   //printch(q); // direct use this can pass, but lt->printch(q) can not
,why?

   while(true); // test perpose loop

}

***********************************
// Terminal.h

#ifndef __TERMINAL_H_
#define __TERMINAL_H_

class Terminal{ // this is virtual class of terminal
 public:

  /* <--- comment for test perpose since can not pass the complie
  virtual void printch(char) = 0;
  virtual void backSpace() = 0;
  virtual void printCR() = 0;
  virtual void printTab() = 0;
  */

};

#endif // __TERMINAL_H_

***********************************
// LinuxTerminal.h

#ifndef __LINUXTERMINAL_H_
#define __LINUXTERMINAL_H_

#include "Terminal.h"

class LinuxTestTerminal : public Terminal{
public:

  void printch(char ch);
  void backSpace();
  void printCR();
  void printTab();

};

#endif // __LINUXTERMINAL_H_

****************************************
// LinuxTerminal.cpp

#include "LinuxTestTerminal.h" // this time, add this line

void
LinuxTestTerminal::printch(char ch){
  fprintf(stdout,"%c",ch);
}

void
LinuxTestTerminal::backSpace(){
   fprintf(stdout,"/b")
}

void
LinuxTestTerminal::printCR(){
  fprintf(stdout,"/n");
}

void
LinuxTestTerminal::printTab(){
  fprintf(stdout,"/t");
}