View Compilation Error

140702_0_13458.cpp: In function `int main()':
140702_0_13458.cpp:5: error: `A' undeclared (first use this function)
140702_0_13458.cpp:5: error: (Each undeclared identifier is reported only once for each function it appears in.)
140702_0_13458.cpp:5: error: `B' undeclared (first use this function)