View Compilation Error

355938_0_10130.cpp: In function `int main()':
355938_0_10130.cpp:15: error: `strlen' undeclared (first use this function)
355938_0_10130.cpp:15: error: (Each undeclared identifier is reported only once for each function it appears in.)
355938_0_10130.cpp:22: error: `abs' undeclared (first use this function)
355938_0_10130.cpp:24: error: `strcpy' undeclared (first use this function)