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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>page_583</title> <link rel="stylesheet" href="reset.css" type="text/css" media="all"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body> <table summary="top nav" border="0" width="100%"> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_582.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_583</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_584.html">next page ></a></td> </tr> <tr> <td align="left" colspan="3" style="background: #ffffff; padding: 20px;"> <table border="0" width="100%" cellpadding="0"><tr><td align="center"> <table border="0" cellpadding="2" cellspacing="0" width="100%"><tr><td align="left"></td> <td align="right"></td> </tr></table></td></tr><tr><td align="left"><p></p><table border="0" cellspacing="0" cellpadding="0" width="100%"><tr><td align="right"><font face="Times New Roman, Times, Serif" size="2" color="#FF0000">Page 583</font></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">The integral types in C++ are </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">char</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">short</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">int</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">long</font><font face="Times New Roman, Times, Serif" size="3">, and </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">enum</font><font face="Times New Roman, Times, Serif" size="3">. The most commonly used integral types are </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">int</font><font face="Times New Roman, Times, Serif" size="3"> and </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">char</font><font face="Times New Roman, Times, Serif" size="3">. The </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">char</font><font face="Times New Roman, Times, Serif" size="3"> type can be used for storing small (one-byte) numeric integers or, more often, for storing character data. Character data include both printable and nonprintable characters. Nonprintable charactersthose that control the behavior of hardware devicesare expressed in C++ as escape sequences such as </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">\n</font><font face="Times New Roman, Times, Serif" size="3">. Each character is represented internally as a nonnegative integer according to the particular character set (such as ASCII or EBCDIC) that a computer uses.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">The floating point types built into the C++ language are </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">double</font><font face="Times New Roman, Times, Serif" size="3">, and </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">long聽double</font><font face="Times New Roman, Times, Serif" size="3">. Floating point numbers are represented in the computer with a mantissa and an exponent. This permits the use of numbers that are much larger or much smaller than those that can be represented with the integral types. Floating point representation also allows us to perform calculations on numbers with fractional parts.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">Representational errors can affect the accuracy of a program's computations. When using floating point numbers, keep in mind that if two numbers are vastly different from each other in size, adding or subtracting them may give inaccurate results. Remember, also, that the computer has a limited range of numbers that it can represent. If a program tries to compute a value that is too large or too small, an error message may result when the program executes.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">C++ allows the programmer to define additional data types. The Typedef statement is a simple mechanism for renaming an existing type, although the result is not truly a new data type. An enumeration type, created by listing the identifiers that make up the domain, is a new data type that is distinct from any existing type. Values of an enumeration type may be assigned, compared in relational expressions, used as case labels in a Switch statement, and returned as function values. Enumeration types are extremely useful in the writing of clear, self-documenting programs. In succeeding chapters, we look at language features that let us create even more powerful user-defined types.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3"><i>Quick Check</i></font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">1. The C++ simple types are divided into integral types and floating point types. What are the five integral types (ignoring the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">unsigned</font><font face="Times New Roman, Times, Serif" size="3"> variations) and the three floating point types? (pp. 502503)</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">2. What is the difference between an expression and an expression statement in C++?(pp.510513)</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Times New Roman, Times, Serif" size="3">3. Assume that the following code segment is executed on a machine that uses the ASCII character set. What is the final value of the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">char</font><font face="Times New Roman, Times, Serif" size="3"> variable </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">someChar?</font><font face="Times New Roman, Times, Serif" size="3"> Give both its external and internal representations. (pp. 517520)</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"></td> <td colspan="3" height="12"></td> <td rowspan="5"></td></tr><tr><td colspan="3"></td></tr><tr><td></td> <td><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">someChar聽=聽T;<br />someChar聽=聽someChar聽+聽4;</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table></td></tr></table><p><font size="0"></font></p>聽 </td> </tr> <tr> <td align="left" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_582.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_583</strong></td> <td align="right" width="30%" style="background: #EEF3E2"><a style="color: blue; font-size: 120%; font-weight: bold; text-decoration: none; font-family: verdana;" href="page_584.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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