Explain the code from line 1- line 17

EXAMPLE 2-29 // Author: D.S. Malik // This program shows where the include s. // statements, .taments, using t, named constants, variable declarations and input and output statements typi ns, assignment ltx*t t xxiiatt #include //Line 1 using namespace std; const int NUMBER = 12; int main() //Line 2 //Line 3 //Line 4 //Line 5 //Line 6 //Line 7 int firstNum; int secondNum //Line 8 firs tNur 18; cout > secondNum; cout