= The C Programming Language: A Tutorial =

= History =

C was developed by Dennis Ritchie in 1969 in order to write the Unix operating system.

At that time Unix was written in assembly language. Because assembly language differs between processors, every new kind of processor needed a new operating system. C forms a portable abstraction over the assembly language.

Because C is a minimalistic langauge, C compilers are relatively easy to write. Because C produces fairly efficient assembly code, it's possible to write fast programs in C. For these reasons, C became very popular, and today pretty much every operating system and many other programs are written in C.

= What C Is Used For =

C is used to write both operating system kernels, the piece of software that mediates access to the hardware, and low level system libraries. C is also heavily used in embedded development.

Because by default C has no garbage collector and has a very minimalistic runtime, it is ideal for situations where space and time requirements are tight.

C is a good choice for libraries because most higher level languages know how to call C functions and use C datastructures.

C is also used in a vast swath of legacy code, due to its historical popularity. Knowing C is useful for working with many of the large code bases in existence.

Because C has been standardized for a long time, it is probably the most portable programming language. C runs on many platforms for which there are no other programming languages.

= What You Shouldn't Use C For =

C is an extremely minimalistic and low level language. It has no garbage collector by default. It also does not do much to prevent the programmer from shooting himself in a foot.

For this reason, unless you have a specific need for C, you should pick a higher level language.

Good higher level languages include: Python, Lisp, Ruby, Javascript, ML

Computers are extremely fast these days, so usually performance requirements are very loose. For instance, Python is very slow, but it almost always does not matter.

= C89, C99, and GNU C =

== C89 ==

In 1989 C was standardized by the International Standards Organization (ISO). Almost all C compilers have a very complete implementation of the C89 standard. You can purchase the standard from ISO or ANSI:

http://webstore.ansi.org/RecordDetail.aspx?sku=AS%203955-1991

== C99 ==

In 1999 a new C standard was written. Some C99 extensions are widely implemented in compilers, but some have largely been ignored. Projects that want maximum portability either restrict themselves to C89, or avoid using C99 constructs that aren't widely implemented.

http://webstore.ansi.org/RecordDetail.aspx?sku=ISO/IEC+9899:1999

== How To Use Standards ==

These standard documents are not good for learning C, but they are good to have when you are doing real C programming. If you need to look up some function or syntax in C, the C89 standard gives you an complete reference that is by definition NEVER WRONG. That is quite valuable.

== GNU C ==

GNU C is the implementation of C provided by the GCC compiler. It provides many extensions to C. Much of C99 was based on extensions provided by GNU C. GNU C does not implement all C99 features.

In this tutorial I have used a few C99 features. In particular, C89 requires that all variables be declared in a block before any other actions are performed.

void f() { int x = 0 int y = 0; int z = 0;

 /* other statements*/
 x = g();

}

However, C99 allows you to mix declarations and other actions, which I prefer.

void f() { int x = g(); int y = 0; int z = 0; }

= C++ and C++0x =

C++ is a language derived from C. While C is minimalistic, C++ provides many features including:

1. templates
2. better memory management through RAII techniques
3. exceptions for error handling
4. operating overloading
5. namespaces
6. object orientation
7. a much larger standard library with common datastructure and algorithms

C++0x is a new standard for C++ that adds even more features:

1. better support for functional programming with lambdas
2. more efficiency with R value references and move constructors
3. a standard multithreading library
4. better support for template programming
5. more datastructures and algorithms
6. more and better smart pointers
7. lots of miscelanious improvements and fixes

http://en.wikipedia.org/wiki/C%2B%2B0x

C++ is derived from C, but the C programming style is not appropriate in C++. In fact, exceptions will break some patterns common in C programming.

This tutorial is geared towards learning C++ as a next step. For that reason I try to point out places where a C construct is a bad idea in C++, or if C++ provides a better alternative.

= Further Reading =

The most recommended book for learning C is The C Programming Language by Kernigan and Ritchie. Ritchie is the author of the language itself.

http://www.amazon.com/Programming-Language-2nd-Brian-Kernighan/dp/0131103628

Remember when you start writing real world C programs to get a copy of the C89 standard.

http://webstore.ansi.org/RecordDetail.aspx?sku=AS%203955-1991