C++ Programming/Programming Languages/Comparisons/C

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[edit] C 89/99

C was essentially the core language of C++ when Bjarne Stroustrup, decided to create a "better C". Many of the syntax conventions and rules still hold true and so we can even state that C was a subset of C++, most recent C++ compilers will also compile C code taking into consideration the small incompatibilities, since C99 and C++ 2003 are not compatible any more. You can also check more information about the C language on the C Programming Wikibooks ( http://en.wikibooks.org/wiki/C ).

C++ as defined by the ANSI standard in 98 (called C++98 at times) is very nearly, but not quite, a superset of the C language as it was defined by its first ANSI standard in 1989 (known as C89). There are a number of ways in which C++ is not a strict superset, in the sense that not all valid C89 programs are valid C++ programs, but the process of converting C code to valid C++ code is fairly trivial (avoiding reserved words, getting around the stricter C++ type checking with casts, declaring every called function, and so on).

In 1999, C was revised and many new features were added to it. As of 2004, most of these new "C99" features are not there in C++. Some (including Stroustrup himself) have argued that the changes brought about in C99 have a philosophy distinct from what C++98 adds to C89, and hence these C99 changes are directed towards increasing incompatibility between C and C++.

The merging of the languages seems a dead issue as coordinated actions by the C and C++ standards committees leading to a practical result didn't happen and it can be said that the languages started even to diverge.

Some of the differences are:

• C++ supports function overloading (absent in C89, allowed only for some standard library code in C99).
• C++ supports inheritance and polymorphism.
• C++ adds keyword class, but keeps struct from C, with compatible semantics.
• C++ supports access control for class members.
• C++ supports generic programming through the use of templates.
• C++ extends the C89 standard library with its own standard library.
• C++ and C99 offer different complex number facilities.
• C++ has bool and wchar_t as primitive types, while typedefs in C.
• C++ comparison operators return bool, while C returns int.
• C++ supports overloading of operators.
• C++ character constants have type char, while C character constants have type int.
• C++ has additional cast operators (static_cast, dynamic_cast, const_cast and reinterpret_cast).
• C++ adds mutable keyword to address the imperfect match between physical and logical constness.
• C++ extends the type system with references.
• C++ supports member functions, constructors and destructors for user-defined types to establish invariants and to manage resources.
• C++ supports runtime type identification (RTTI), via typeid and dynamic_cast.
• C++ includes exception handling.
• C++ has std::vector as part of its standard library instead of variable-length arrays as in C.
• C++ treats sizeof operator as compile time operation, while C allows it be a runtime operation.
• C++ has new and delete operators, while C uses malloc and free library functions exclusively.
• C++ supports object-oriented programming without extensions.
• C++ does not require use of macros and careful information-hiding and abstraction for code portability.
• C++ supports per-line comments denoted by //. (C99 started official support for this comment system, and most compilers supported this as an extension.)

[edit] Reasons to chose one of the languages over the other

It is not uncommon to find someone defending C over C++ or vice versa or complain about some of those languages features. There is no scientific evidence to put most languages above another in general terms, the only reasons that do have some traction is if the language is still very recent and prone to deep changes or as yet unknown bugs, in the case of C or C++ this is not the case both languages are very mature even if both are still evolving, the new features keep an high level of compatibility with old code, making the use of those new constructs a programmer's decision. It is not uncommon to establish rules in a project to limit the use of parts of a language (such as RTTI, exceptions, or virtual-functions in inner loops), due the proficiency of the programmers or the needs of the project, as it is also common for new hardware to support lower level languages first. Due to C being less extensive and lower level than C++, it is easier to check and comply with strict industry guidelines and automate those steps. Another benefit is that it is easier for the programmer to do low level optimizations, even if most C++ compilers can guarantee near perfect optimizations automatically, a human can still do more and C has less complex structures.

Any of the valid reasons to choose a language over another is mostly due to programmers choice that indirectly deals with choosing the best tool for the job and having the resources needed to complete it. It would be hard to validate selecting C++ for a project if the available programmers only knew C or even the reverse, it is somewhat expected for a C++ programmer to produce functional C code, but the mindset and experience needed aren't the same, the same rational is valid for C programmers and ASM, this is due to the close relations that exist in the language structure and historic evolution.

One could argue that using the C subset of C++, in a C++ compiler, is the same as using C but in reality we find that it will generate slightly different results depending on the compiler used.