View Compilation Error

0_0_35511415_24176.cpp: In function 'int main()':
0_0_35511415_24176.cpp:3:5: error: 'pid_t' was not declared in this scope
     pid_t fpid; //fpid表示fork函数返回的值
     ^
0_0_35511415_24176.cpp:5:5: error: 'fpid' was not declared in this scope
     fpid=fork();
     ^
0_0_35511415_24176.cpp:5:15: error: 'fork' was not declared in this scope
     fpid=fork();
               ^
0_0_35511415_24176.cpp:9:71: error: 'getpid' was not declared in this scope
         printf("i am the child process, my process id is %d/n",getpid());
                                                                       ^
0_0_35511415_24176.cpp:14:72: error: 'getpid' was not declared in this scope
         printf("i am the parent process, my process id is %d/n",getpid());
                                                                        ^