stdio vs iostream [closed]

Answer 1

Using iostream should not make your program crash. It can be slow, but that's only because it's trying to interoperate with stdio. That synchronization can be turned off¹. iostream is the idiomatic C++ way to get input, and I'd recommend its use over stdio functions in most cases when using C++.

¹ using std::ios::sync_with_stdio(false);

Answer 2

Use streams in C++ and stdio.h in C. Yes, streams are a bit slower, but do those milliseconds count? User input is rarely a bottleneck of an application.

And if streams are used properly, and your compiler/runtime libraries are ok, your application won't crash.

But, if you have good, explainable reasons to use cstdio functions, then it is fully legitimate to use them in C++ as well.

Answer 3

Unless performance of the I/O REALLY matters, use whichever makes your program the clearest (easiest to read).

In the vast number of programs I've written, only a few have needed special treatment to "how fast the I/O is" - and most of the problem with std::stream functions has to to with the actual parsing of the input [as well as sync with stdio] - which, if you are reading, say, floating point numbers, will be quite difficult to write your own version of [that accepts the full range of formats that std::stream allows].

If I/O performance REALLY matters, then using std::stream::read and std::stream::write may be the solution, but in most cases, best performance comes from using the non-portable mmap and MapViewOfFile interfaces that "map" the contents of a file directly from the filesystem to the virtual memory of the application. This saves on the amount of copying the processing of the data takes, and will make it a little faster.

Answer 4

The iostreams library probably is slower than the lower-level stdio library. Streams does a lot more under the covers - type conversions, localization, exception handling, etc.