(linux/g++)redefinition에러가 발생합니다

choijongin@choijongin-VirtualBox:~/OSS$ g++ JOS.cpp Desktop.cpp Box.cpp
JOS.cpp: In function ‘bool SetValidPos(int*, int*)’:
JOS.cpp:100:6: error: redefinition of ‘bool SetValidPos(int*, int*)’
 bool SetValidPos(int * _x, int * _y)
      ^~~~~~~~~~~
JOS.h:20:6: note: ‘bool SetValidPos(int*, int*)’ previously defined here
 extern bool SetValidPos(int * _x, int * _y);
      ^~~~~~~~~~~
JOS.cpp: In function ‘void Draw(int, int, const char*)’:
JOS.cpp:116:6: error: redefinition of ‘void Draw(int, int, const char*)’
 void Draw(int _x, int _y, const char * _c)
      ^~~~
JOS.h:36:6: note: ‘void Draw(int, int, const char*)’ previously defined here
JOS.cpp: In function ‘void Draw(int, int, char*)’:
JOS.cpp:123:6: error: redefinition of ‘void Draw(int, int, char*)’
 void Draw(int _x, int _y, char * _c)
      ^~~~
JOS.h:43:6: note: ‘void Draw(int, int, char*)’ previously defined here
JOS.cpp: In function ‘void Draw(int, int, char)’:
JOS.cpp:130:6: error: redefinition of ‘void Draw(int, int, char)’
 void Draw(int _x, int _y, char _c)
      ^~~~
JOS.h:50:6: note: ‘void Draw(int, int, char)’ previously defined here
JOS.cpp: In function ‘int Kbhit()’:
JOS.cpp:140:5: error: redefinition of ‘int Kbhit()’
 int Kbhit(void)
     ^~~~~
JOS.h:60:5: note: ‘int Kbhit()’ previously defined here

#pragma once
 
#include <iostream>
#include <string.h>
#include <cstring>
#include <termios.h>
#include <unistd.h>
#include <fcntl.h>
 
 
#define SIZEX 144       // 최상위 윈도우 사이즈
#define SIZEY 36        // 최상위 윈도우 사이즈
 
using namespace std;
 
 
extern char g_backBuffer[SIZEY+1][SIZEX+1][4];  // 후면버퍼
 
//화면 밖을 벗어나는 좌표가 들어오면 값을 화면 안으로 수정하고 거짓을 반환
extern bool SetValidPos(int * _x, int * _y);
// 화면에 특정 문자를 특정 위치에 출력, 조만간 텍셀이라는 구조체를 만들 예정
extern void Draw(int _x, int _y, const char * _c);
extern void Draw(int _x, int _y, char * _c);
extern void Draw(int _x, int _y, char _c);
// 키보드 버퍼가 비어있지 않으면 1을 반환
extern int Kbhit(void);
// 윈도우 있는 Kbhit 함수를 쓸수 없어서 구글에서 검색해서 사용함 출처 >> <a href="https://corsa.tistory.com/18" rel="nofollow">https://corsa.tistory.com/18</a> [CORSA]
extern void Gotoxy(int x, int y);