View Compilation Error

0_0_6143446_28401.cpp: In function `int main()':
0_0_6143446_28401.cpp:35: error: `toupper' undeclared (first use this function)
0_0_6143446_28401.cpp:35: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6143446_28401.cpp:35: error: `tolower' undeclared (first use this function)