bottom…up。 o Within an architecture； individual pieces are called ponents； and they fit together to create a plete application。 o You write tests because you cannot verify the functionality of a ponent based on its identifier； parameters； or return value。 o When implementing ponents； you develop tests before； during； and after writing the source code。 o A test is a piece of source code that calls a ponent using targeted input data； and the results from the ponent are verified with targeted responses。 If the results do not match the targeted responses； the ponent has failed。 o The CLR offers many different data types； with the major distinction being between value and reference types。 o The CLR has many different number types； but all number types are value types。 o Numbers can overflow or underflow。 You should activate a piler setting to make sure that the CLR will catch those situations。 o When deciding on a specific number type； a large part of the decision is based on how much precision is desired。 Some Things for You to Do The following are some things to consider related to what you’ve learned in this chapter： 1。 When you write code； how should you organize your code？ For example； do you enforce certain naming conventions for your classes？ Do you enforce the use of code ments？ 2。 In the development munity； there is a discussion of whether organization of your software should involve formal structures or should be ad hoc。 Think about how software should be organized。 3。 In general； how would you test whether or not a ponent that uses a database worked properly？ Outline the process with bulleted points。 …………………………………………………………Page 71…………………………………………………………… CH A PT E R 2 ■ L E A R N I N G A B OU T 。 N E T N U M B E R AN D V A L U E T Y P E S 49 4。 In general； how would you test the correctness of writing data to a file？ To help under stand the nature of the problem； how do you know that an operating system manipulates files properly？ 5。 If the CLR did not provide for a mechanism to catch overflow and underflow conditions； how would you ensure that overflow and underflow didn’t happen？ 6。 For a Pentium CPU （32 bits）； which number type would result in the fastest calculations？ 7。 In this chapter’s example； the class Operations is designed to perform arithmetic using the Double type。 How would you change this so that the calculations are generic and don’t rely on the Double type？ …………………………………………………………Page 72…………………………………………………………… …………………………………………………………Page 73…………………………………………………………… C H A P T E R 3 ■ ■ ■ Learning About String Manipulations In the previous chapter； you learned the basics of how data is stored and managed by ； including the difference between value and reference types。 has three major data types： number…related； custom…defined； and String。 The previous chapter focused on the number related types。 This chapter will focus on the String type。 As you’ll learn in this chapter； the String type has some special characteristics。 If you were to look at the bits and bytes of the String type； you would not realize that they were letters。 In an abstract description； a String type is a number type with a special grammar。 Since a puter understands only numbers； it uses lookup tables that map a set of letters to a set of numbers。 The example in this chapter is a multilingual translation program。 The translation program will not be sophisticated； nor will it be capable of much。 However； it will illustrate many of the issues that you will be confronted with when working with strings。 Organizing the Translation Application As emphasized in the previous chapter； the first step in developing an application is to get organized。 We need to understand and define the features of the sample application we are going to develop。 The multilingual translation program will implement the following features： o Translate greetings into three different languages： French； German； and English。 o Convert numbers into the three different languages。 o Convert a date into the three different languages。 From a feature perspective； the first feature is logical； but the second and third features are not as obvious。 We generally think of translation as translating one word to another word（s）。 Yet； languages also can represent numbers and dates in different ways。 Translation will mean two things： translate a word from one language to another； and translate a number or date from one language to another。 As in Chapter 2； we’ll create the solution as ponents with three pieces： a Windows application； a testing console application； and a class library。 After you have created each of the projects； your workspace should look like Figure 3…1。 Remember to add a reference to the 51 …………………………………………………………Page 74…………………………………………………………… 52 CH AP T E R 3 ■ L E A R N IN G AB OU T ST R I N G M A N I P U L AT IO N S LanguageTranslator class library （right…click TestLanguageTranslator and choose Add Reference Projects LanguageTranslator）。 Also remember to set TestLanguageTranslator as the startup project。