View Compilation Error

0_0_5437140_2308.cpp: In function `int main()':
0_0_5437140_2308.cpp:4: error: `scanf' undeclared (first use this function)
0_0_5437140_2308.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_5437140_2308.cpp:8: error: `a' undeclared (first use this function)
0_0_5437140_2308.cpp:9: error: `b' undeclared (first use this function)
0_0_5437140_2308.cpp:10: error: `strlen' undeclared (first use this function)
0_0_5437140_2308.cpp:20: error: `printf' undeclared (first use this function)