View Compilation Error

0_0_9566130_19494.cpp: In function `int main()':
0_0_9566130_19494.cpp:16: error: `toupper' undeclared (first use this function)
0_0_9566130_19494.cpp:16: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_9566130_19494.cpp:24: error: `tolower' undeclared (first use this function)