View Compilation Error

0_0_1734456_7782.cpp: In function `void add()':
0_0_1734456_7782.cpp:27: error: `strrev' undeclared (first use this function)
0_0_1734456_7782.cpp:27: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1734456_7782.cpp: In function `int main()':
0_0_1734456_7782.cpp:43: error: `strrev' undeclared (first use this function)