View Compilation Error

0_0_4186489_6191.cpp: In function `node* build()':
0_0_4186489_6191.cpp:12: error: `NULL' undeclared (first use this function)
0_0_4186489_6191.cpp:12: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_4186489_6191.cpp: In function `void insert(char*, int)':
0_0_4186489_6191.cpp:21: error: `NULL' undeclared (first use this function)
0_0_4186489_6191.cpp: In function `int query(char*)':
0_0_4186489_6191.cpp:31: error: `NULL' undeclared (first use this function)
0_0_4186489_6191.cpp: In function `int main()':
0_0_4186489_6191.cpp:40: error: `scanf' undeclared (first use this function)
0_0_4186489_6191.cpp:40: error: `EOF' undeclared (first use this function)
0_0_4186489_6191.cpp:52: error: `printf' undeclared (first use this function)