View Compilation Error

0_0_8121722_13896.cpp: In function `int tf(char*)':
0_0_8121722_13896.cpp:10: error: `isdigit' undeclared (first use this function)
0_0_8121722_13896.cpp:10: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_8121722_13896.cpp:16: error: `isalpha' undeclared (first use this function)