• Edit: incorrect.

"There is no way to speed up compilation time" from the above comment is not correct. Many people use <bits/stdc++.h>, but few know the real purpose for this file: it is not there to save typing, it is there to save compilation time.

By using stdc++.h, you can create a precompiled header file that includes the whole standard library. Next time you run the compiler, it does not need to parse the standard library headers again — it just reads the precompiled header file instead.

You can read how to create and use the precompiled header here: https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_headers.html#manual.intro.using.headers.pre. After this, compilation time of an empty program should be significantly reduced.