C vs C++ vs Objective-C vs etc

Many computer users may be confused about the differences between C, C++, C#, Objective-C, and others. Thankfully, the differences are easy to understand.

To begin, C is a general-purpose low-level imperative procedural programming language. C source code is compiled and does not object-oriented. Libraries are "imported" using code like #include <stdio.h> or #include "local_lib.h". Headers use the "*.h" file-extension while the primary source code uses "*.c".

Many dialects of C are available such as Cyclone, Unified Parallel C, Split-C, Cilk, and C*. The differences between programming dialects is analogous to the differences between dialects of spoken languages (such as American-English and British-English).

The various C standards (versions) include ANSI C (ISO C), C89, C90, C99, C11, Embedded C, and MISRA C. These standards are different versions of C, just as there is Old-English (Anglo-Saxon), Middle English, Early Modern English, and Modern English (New English). Some versions of C do not support certain dialects.

C++ (isocpp.org) is C with additional features, like object-orientation, additional keywords, and the Standard Template Library (STL). C++ also uses a different method for including headers; the file-extension is dropped and "c" is added to the beginning of names of standard-C libraries. For instance, #include <stdio.h> would be written as #include <cstdio>. File-extensions for C++ code include "*.cc", "*.cpp", "*.cxx", "*.C", and "*.c++"; header file-extensions include "*.h", "*.hh", "*.hpp", "*.hxx",  and "*.h++". Most (or all) C code will compile successfully using a C++ compiler. C++ supports all features used in C. See http://www.cs.fsu.edu/~myers/c++/notes/cdiff.html for more information.

Objective-C (developer.apple.com/library/mac/navigation) is C with the addition of object-oriented programming and Smalltalk-style messaging ([obj method:argument];). Also, Objective-C is a strict superset of C and a thin layer on top of C. Header files use the "*.h" file-extension, and primary source code files use the extension "*.m". Objective-C also adds #import which is like #include without the need for include-guards.

Objective-C++ is C++ with the addition of object-oriented programming and Smalltalk-style messaging ([obj method:argument]; is like obj->method(argument);). Header files use the "*.h" file-extension, and primary source code files use the extensions "*.mm" and "*.C".

According to Wikipedia, these differences are also present.

• A C++ class cannot derive from an Objective-C class and vice versa
• C++ namespaces cannot be declared inside an Objective-C declaration
• Objective-C declarations may appear only in global scope, not inside a C++ namespace
• Objective-C classes cannot have instance variables of C++ classes that do not have a default constructor or that have one or more virtual methods, but pointers to C++ objects can be used as instance variables without restriction (allocate them with new in the -init method).
• C++ "by value" semantics cannot be applied to Objective-C objects, which are only accessible through pointers.
• An Objective-C declaration cannot be within a C++ template declaration and vice versa. However, Objective-C types, (e.g., Classname *) can be used as C++ template parameters.
• Objective-C and C++ exception handling is distinct; the handlers of each cannot handle exceptions of the other type. This is mitigated in recent runtimes as Objective-C exceptions are either replaced by C++ exceptions completely (Apple runtime), or partly when Objective-C++ library is linked (GNUstep libobjc2).
• Care must be taken since the destructor calling conventions of Objective-C and C++’s exception run-time models do not match (i.e., a C++ destructor will not be called when an Objective-C exception exits the C++ object’s scope). The new 64-bit runtime resolves this by introducing interoperability with C++ exceptions in this sense.
• Objective-C blocks and C++11 lambdas are distinct entities, however a block is transparently generated on Mac OS X when passing a lambda where a block is expected.

FUN FACT: At the time of writing this, only GNU-GCC and Clang support Objective-C and Objective-C++.

C-- or "C Minus" (http://www.cs.tufts.edu/~nr/c--/index.html) is a imperative language that is like C, but without many features (hence "C--"). C-- is sometimes called a "portable assembly language".

C#, C♯, or C-Sharp is a strongly typed, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming language. C# is like C++, but with many additions and a Common Language Infrastructure (CLI). C# code uses the "*.cs" file-extension. See https://en.wikipedia.org/wiki/C_Sharp_syntax for more information on C#.

XC is a concurrent, parallel, imperative programming language intended for real-time embedded parallel processors. This C-language is primarily intended for the XMOS XCore processor (a 32-bit RISC microprocessor). The source-code's file-extension is "*.xc". Code written like par { f(); g(); } would be executed in parallel. "Channels" can be used for communication using the send (<:) and receive (:>) operators. XC was influenced by the occam programming language.

Cω or C-Omega is an event-driven language that is an extension of C#. Cω also offers concurrency and datastore data-types (such as XML documents and databases). Polyphonic C# is an extension of C# with concurrency. However, Polyphonic C# was merged with Cω. See http://research.microsoft.com/en-us/um/cambridge/projects/comega/ for more information. To use Cω in C#, import the Cω library using the code using Microsoft.Comega;. Cω is supported by many C# compilers.

μC++ or UC++ is an extension of C++ with concurrency, coroutines, and additional features. This language has additional reserved keywords such as _Resume and _Coroutine. See http://plg.uwaterloo.ca/~usystem/uC++.html for more information.

C* is an object-oriented and data-parallel form of C designed by the company Thinking Machines.

Dataparallel-C is a form of C with parellel-extensions designed by Hatcher and Quinn of the University of New Hampshire.

Some languages that are similar to C and/or C++ include GoLang, Limbo, Alef, D, and Vala. Vala can output C code.

Further Reading

• List of Programming Articles - https://dcjtech.info/topic/programming-and-development/
• Standard C Libraries - https://dcjtech.info/topic/standard-c-libraries/
• Standard C Library Headers - https://dcjtech.info/topic/standard-c-library-headers/