计算机C语言专业外文翻译

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1、4856单词，8230汉字C#  A History of C, C+, and C#   The C# programming language was created in the spirit of the C and C+ programming  languages. This accounts for its powerful features and easy learning curve. The same can't be  said for C and C+, but because C# was created from t

2、he ground up, Microsoft took the  liberty of removing some of the more burdensome features such as pointers. This section  takes a look at the C and C+ languages, tracing their evolution into C#.   The C programming language was originally designed for use on the UNIX operating system

3、.  C was used to create many UNIX applications, including a C compiler, and was eventually  used to write UNIX itself. Its widespread acceptance in the academic arena expanded to  include the commercial world, and software vendors such as Microsoft and Borland released  C compile

4、rs for personal computers. The original Windows API was designed to work with  Windows code written in C, and the latest set of the core Windows operating system APIs  remain compatible with C to this day.   From a design standpoint, C lacked a detail that other languages such as Smal

5、ltalk had already  embraced: the concept of an object. You'll learn more about objects in Chapter 8, " Writing  Object-Oriented Code." For now, think of an object as a collection of data and a set of  operations that can be performed on that data. Object-style coding cou

6、ld be accomplished  using C, but the notion of an object was not enforced by the language. If you wanted to      structure your code to resemble an object, fine. If you didn't, fine. C really didn't care. Objects  weren't an inherent part of the language, so many

7、 people didn't pay much attention to this  programming paradigm.   After the notion of object-oriented development began to gain acceptance, it became clear that  C needed to be refined to embrace this new way of thinking about code. C+ was created to  embody this refinement.

8、 It was designed to be backwardly compatible with C (such that all C  programs would also be C+ programs and could be compiled with a C+ compiler). The  major addition to the C+ language was support for this new object concept. The C+  language added support for classes (which are &qu

9、ot;templates" of objects), and enabled an entire  generation of C programmers to think in terms of objects and their behavior.   The C+ language is an improvement over C, but it still has some disadvantages. C and C+  can be hard to get a handle on. Unlike easy-to-use languages l

10、ike Visual Basic, C and C+ are  very "low level" and require you to do a lot of coding to make your application run well. You  have to write your own code to handle issues such as memory management and error  checking. C and C+ can result in very powerful applications, but y

11、ou need to ensure that  your code works well. One bug can make the entire application crash or behave unexpectedly.  Because of the C+ design goal of retaining backward compatibility with C, C+ was unable  to break away from the low level nature of C.   Microsoft designed C# to r

12、etain much of the syntax of C and C+. Developers who are  familiar with those languages can pick up C# code and begin coding relatively quickly. The  big advantage to C#, however, is that its designers chose not to make it backwardly  compatible with C and C+. While this may seem like

13、 a bad deal, it's actually good news. C#  eliminates the things that makes C and C+ difficult to work with. Because all C code is also  C+ code, C+ had to retain all of the original quirks and deficiencies found in C. C# is  starting with a clean slate and without any compatibilit

14、y requirements, so it can retain the  strengths of its predecessors and discard the weaknesses that made life hard for C and C+  programmers.   Introducing C#   C#, the new language introduced in the .NET Framework, is derived from C+. However, C#  is a modern, objected-orie

15、nted (from the ground up) type-safe language.   Language features   The following sections take a quick look at some of the features of the C# language. If some  of these concepts don't sound familiar to you, don't worry. All of them are covered in detail in  later chapte

16、rs.   Classes   All code and data in C# must be enclosed in a class. You can't define a variable outside of a  class, and you can't write any code that's not in a class. Classes can have constructors, which  execute when an object of the class is created, and a destru

17、ctor, which executes when an  object of the class is destroyed. Classes support single inheritance, and all classes ultimately  derive from a base class called object. C# supports versioning techniques to help your classes      evolve over time while maintaining compatibilit

18、y with code that uses earlier versions of your  classes.   As an example, take a look at a class called Family. This class contains the two static fields  that hold the first and last name of a family member as well as a method that returns the full  name of the family member. &n

19、bsp; class Class1    public string FirstName；  public string LastName；  public string FullName()      return FirstName + LastName；    Note Single inheritance means that a C# class can inherit from only one base class.   C# enables you to group your c

20、lasses into a collection of classes called a namespace.  Namespaces have names, and can help organize collections of classes into logical groupings.  As you begin to learn C#, it becomes apparent that all namespaces relevant to the .NET  Framework begin with System. Microsoft has also

21、 chosen to include some classes that aid in  backwards compatibility and API access. These classes are contained within the Microsoft  namespace.   Data types   C# lets you work with two types of data: value types and reference types. Value types hold  actual values. Referen

22、ce types hold references to values stored elsewhere in memory.  Primitive types such as char, int and float, as well as enumerated values and structures, are  value types. Reference types hold variables that deal with objects and arrays. C# comes with  predefined reference types (obje

23、ct and string), as well as predefined value types (sbyte, short,  int, long, byte, ushort, uint, ulong, float, double, bool, char, and decimal). You can also define  your own value and reference types in your code. All value and reference types ultimately  derive from a base type call

24、ed object.   C# allows you to convert a value of one type into a value of another type. You can work with  both implicit conversions and explicit conversions. Implicit conversions always succeed and  don't lose any information (for example, you can convert an int to a long without

25、 losing any  data because a long is larger than an int). Explicit conversions may cause you to lose data (for  example, converting a long into an int may result in a loss of data because a long can hold  larger values than an int). You must write a cast operator into your code to make

26、 an explicit  conversion happen.  Cross-Reference  Refer to Chapter 3, "Working with Variables," for more information  about implicit and explicit conversions.  You can work with both one-dimensional and multidimensional arrays in C#.  Multidimensional arrays

27、can be rectangular, in which each of the arrays has the same  dimensions, or jagged, in which each of the arrays has different dimensions.      Classes and structures can have data members called properties and fields. Fields are  variables that are associated with the enclosing class or structure. You may define a structure  called Employee, for example, that has a field called Name. If you define a variable of type  Employee called CurrentEmployee, you can retrieve the employee's name by writing