Increase type safety, reduce errors, allow extensibility, and provide
printf() is arguably not broken, and scanf() is perhaps livable despite
being error prone, however both are limited with respect to what C++ I/O can
do. C++ I/O (using << and >>) is, relative to C (using printf() and
- More type-safe: With <iostream>, the type of object being
I/O'd is known statically by the compiler. In contrast, <cstdio> uses
"%" fields to figure out the types dynamically.
- Less error prone: With <iostream>, there are no
redundant "%" tokens that have to be consistent with the actual objects
being I/O'd. Removing redundancy removes a class of errors.
- Extensible: The C++ <iostream> mechanism allows new
user-defined types to be I/O'd without breaking existing code. Imagine the
chaos if everyone was simultaneously adding new incompatible "%" fields
to printf() and scanf()?!
- Inheritable: The C++ <iostream> mechanism is built from
real classes such as std::ostream and std::istream. Unlike <cstdio>'s
FILE*, these are real classes and hence inheritable. This means you
can have other user-defined things that look and act like streams, yet that do
whatever strange and wonderful things you want. You automatically get to use
the zillions of lines of I/O code written by users you don't even know, and
they don't need to know about your "extended stream" class.