View Compilation Error

0_0_3064226_16786.cpp: In function `void shift(char*)':
0_0_3064226_16786.cpp:4: error: `strlen' undeclared (first use this function)
0_0_3064226_16786.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_3064226_16786.cpp:6: error: `strchr' undeclared (first use this function)
0_0_3064226_16786.cpp: In function `int main()':
0_0_3064226_16786.cpp:21: error: `strcmp' undeclared (first use this function)