Why are we studying this topic?
Nowadays everyone is busy doing competitive programming and you know that when there is a large number of test-cases, code takes more time to perform the input/output operation and we all know that in competitive programming execution time should be as small as much as possible. So to minimize execution time we use the concept of fast input output.
C++ is a backward-compatible language means C++ synchronizes with C language, that is why C++ supports most syntax of C language. This synchronization of C++ with C consumes time somewhere in the backend. So for fast execution, we have to break this synchronization. For this, we include one extra line :
ios_base::sync_with_stdio(false);
and in C++ there is synchronization between Cin and Cout so brokerage of this synchronization is also necessary for fast code execution . For this, we include one extra line:
cin.tie(NULL);
After include these two lines in our code we can write code with less execution time .