Encyclopedia of Computer Science and Technology

C++ 67C#Introduced in 2002, C# (pronounced “C sharp”) is a programminglanguage similar to C++ and Java but simplifiedin several respects and tailored for use with Microsoft’slatest programming platform (see Microsoft.net). C# isa general-purpose language and is thoroughly objectoriented—allfunctions must be declared as members ofa class or “struct,” and even fundamental data types arederived from the System.Object class (see class and objectorientedprogramming).Compared with C++, C# is stricter about the use andconversion of data types, not allowing most implicit conversions(such as from an enumeration type to the correspondinginteger—see data structures). Unlike C++,C# does not permit multiple inheritance (where a type canbe derived from two or more base types), thereby avoidingan added layer of complexity in class relationships inlarge software projects. (However, a similar effect can beobtained by declaring multiple “interfaces” or specifiedways of accessing the same class.)Unlike Java (but like C++), C# includes pointers (anda safer version called “delegates”), enumerations (enumtypes), structs (treated as lightweight classes), and overloading(multiple definitions for operators). The latest versionof the language, C# 3.0 (introduced in 2007), providesadditional features for list processing and functional programming(see functional languages).The canonical “Hello World” program looks like this inC#:using System;// A “Hello World!” program in C#namespace HelloWorld{class Hello{static void Main(){System.Console.WriteLine(“Hello World!”);}}}Essentially all program structures must be part of aclass. The first statement brings in the System class, fromwhich are derived basic interface methods. A program canhave one or more namespaces, which are used to organizeclasses and other structures to avoid ambiguity. This programhas only one class (Hello), which includes a Mainfunction (every program must have one and only one). Thisfunction calls the Console member of the System class, andin turn uses the WriteLine method to display the text.C++ and Microsoft DevelopmentC# is part of a family of languages (including C++, J#[an equivalent version of Java], and Visual Basic.NET). Allthese languages compile to a common intermediate language(IL). The common class framework, Microsoft.NET,has replaced earlier frameworks for Windows programmingand, increasingly, for modern Web development (seealso Ajax).Although it has been primarily associated with Microsoftdevelopment and Windows, the Mono and Dot GNUprojects provide C# and an implementation of the CommonLanguage Infrastructure, and many (but not all) of the.NET libraries for the Linux/UNIX environment.Further Reading“The C# Language.” MSDN. Available online. URL: http://msdn2.microsoft.com/en-us/vcsharp/aa336809.aspx. Accessed April28. 2007.Davis, Stephen Randy. C# for Dummies. New York: Hungry Minds,2002.Hejlsberg, Andres, Scott Wiltamuth, and Peter Golde. The C# ProgrammingLanguage. 2nd ed. Upper Saddle River, N.J.: Addison-Wesley,2006.C++The C++ language was designed by Bjarne Stroustrup atAT&T’s Bell Labs in Murray Hill, New Jersey, starting in1979. By that time the C language had become well establishedas a powerful tool for systems programming (seeC). However Stroustrup (and others) believed that C’s limiteddata structures and function mechanism were provinginadequate to express the relationships found in increasinglylarge software packages involving many objects withcomplex relationships.Consider the example of a simple object: a stack ontowhich numbers can be “pushed” or from which they can be“popped” (see stack). In C, a stack would have to be implementedas a struct to hold the stack data and stack pointer,and a group of separately declared functions that couldaccess the stack data structure in order to, for example“push” a number onto the stack or “pop” the top numberfrom it. In such a scheme there is no direct, enforceablerelationship between the object’s data and functions. Thismeans, among other things, that parts of a program couldbe dependent on the internal structure of the object, orcould directly access and change such internal data. In alarge software project with many programmers working onthe code, this invites chaos.An alternative paradigm already existed (see objectorientedprogramming) embodied in a few new languages(see Simula and Smalltalk). These languages allow for thestructuring of data and functions together in the form ofobjects (or classes). Unlike a C struct, a class can containboth the data necessary for describing an object and thefunctions needed for manipulating it (see class). A class“encapsulates” and protects its private data, and communicateswith the rest of the program only through calls to itsdefined functions.Further in object-oriented languages, the principle ofinheritance could be used to proceed from the most general,abstract object to particular versions suited for specifictasks, with each object retaining the general capabilitiesand revising or adding to them. Thus, a “generic” list foundationclass could be used as the basis for deriving a varietyof more specialized lists (such as a doubly-linked list).