View Compilation Error

1_487_815_32627.cpp: In function `int main()':
1_487_815_32627.cpp:6: error: `a' undeclared (first use this function)
1_487_815_32627.cpp:6: error: (Each undeclared identifier is reported only once for each function it appears in.)
1_487_815_32627.cpp:12: error: `scanf' undeclared (first use this function)
1_487_815_32627.cpp:15: error: `printf' undeclared (first use this function)