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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_135</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_134.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_135</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_136.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 135</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">When you enter input data at the keyboard, you must be sure that each data value is appropriate for the data type of the variable in the input statement.</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table cellpadding="0" cellspacing="0" border="0" width="100%"><tr><td height="12"></td></tr><tr><td><table cellspacing="0" width="528" cellpadding="7"><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2"><i>Data Type of Variable In an </i></font><i><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">>></font><font face="Times New Roman, Times, Serif" size="2"> Operation</font></i></td><td valign="bottom"><font face="Times New Roman, Times, Serif" size="2"><i>Valid Input Data</i></font></td></tr><tr><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">char</font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">A single printable character other than a blank</font></td></tr><tr><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">int</font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">An </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">int</font><font face="Times New Roman, Times, Serif" size="2"> literal constant, optionally preceded by a sign</font></td></tr><tr><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">float</font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">An </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">int</font><font face="Times New Roman, Times, Serif" size="2"> or </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">float</font><font face="Times New Roman, Times, Serif" size="2"> literal constant (possibly in scientific, E, notion), optionally preceded by a sign</font></td></tr></table></td></tr></table><br /><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">Notice that when you input a number into a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float</font><font face="Times New Roman, Times, Serif" size="3"> variable, the input value doesn't have to have a decimal point. The integer value is automatically coerced to a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float</font><font face="Times New Roman, Times, Serif" size="3"> value. Any other mismatches, such as trying to input a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float</font><font face="Times New Roman, Times, Serif" size="3"> value into an </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">int</font><font face="Times New Roman, Times, Serif" size="3"> variable or a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">char</font><font face="Times New Roman, Times, Serif" size="3"> value into a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float</font><font face="Times New Roman, Times, Serif" size="3"> variable, can lead to unexpected and sometimes serious results. Later in this chapter we discuss what might happen.</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">When looking for the next input value in the stream, the >> operator skips any leading <i>whitespace characters.</i> Whitespace characters are blanks and certain nonprintable characters like the character that marks the end of a line. (We talk about this end-of-line character in the next section.) After skipping any whitespace characters, the >> operator proceeds to extract the desired data value from the input stream. If this data value is a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">char</font><font face="Times New Roman, Times, Serif" size="3"> value, input stops as soon as a single character is input. If the data value is </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">int</font><font face="Times New Roman, Times, Serif" size="3"> or </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float</font><font face="Times New Roman, Times, Serif" size="3">, input of the number stops at the first character that is inappropriate for the data type, such as a whitespace character. Here are some examples, where </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">i</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">j</font><font face="Times New Roman, Times, Serif" size="3">, and </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">k</font><font face="Times New Roman, Times, Serif" size="3"> are </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">int</font><font face="Times New Roman, Times, Serif" size="3"> variables, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">ch</font><font face="Times New Roman, Times, Serif" size="3"> is a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">char</font><font face="Times New Roman, Times, Serif" size="3"> variable, and </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">x</font><font face="Times New Roman, Times, Serif" size="3"> is a </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">float</font><font face="Times New Roman, Times, Serif" size="3"> variable:</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table><table cellpadding="0" cellspacing="0" border="0" width="100%"><tr><td height="12"></td></tr><tr><td><table cellspacing="0" width="569" cellpadding="7"><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2"><i>Statement</i></font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2"><i>Data</i></font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2"><i>Contents After Input</i></font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2">1. </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">cin聽>>聽i</font><font face="Times New Roman, Times, Serif" size="2"> ;</font></td><td valign="top"><font face="Times New Roman, Times, Serif" size="2">32</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">i</font><font face="Times New Roman, Times, Serif" size="2"> = 32</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2">2. </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">cin聽>>聽i聽>>聽j聽;</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">4聽60</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">i</font><font face="Times New Roman, Times, Serif" size="2"> = 4, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">j</font><font face="Times New Roman, Times, Serif" size="2"> = 60</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2">3. </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">cin聽>>聽i聽>>聽ch聽>>聽x;</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">25聽A聽16.9</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">i</font><font face="Times New Roman, Times, Serif" size="2"> = 25, ch = A, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">x</font><font face="Times New Roman, Times, Serif" size="2"> = 16.9</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2">4. </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">cin聽>>聽i聽>>聽ch聽>>聽x;</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">25</font></td><td valign="top"></td></tr><tr><td valign="top"></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">A</font></td><td valign="top"></td></tr><tr><td valign="top"></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">16.9:</font></td><td valign="bottom"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">i</font><font face="Times New Roman, Times, Serif" size="2"> = 25, ch = A, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">x</font><font face="Times New Roman, Times, Serif" size="2"> = 16.9</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2">5. </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">cin聽>>聽i聽>>聽ch聽>>聽x;</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">25A16.9</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">i</font><font face="Times New Roman, Times, Serif" size="2"> = 25, ch = A, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">x</font><font face="Times New Roman, Times, Serif" size="2"> = 16.9</font></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2">6. </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">cin聽>>聽i聽>>聽j聽>>聽x;</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">12聽8</font></td><td valign="top"><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"><img src="3e26ecb1b6ac508ae10a0e39d2fb98b2.gif" border="0" width="0" height="1" alt="3e26ecb1b6ac508ae10a0e39d2fb98b2.gif" /></td> <td colspan="3" height="1"></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">i</font><font face="Times New Roman, Times, Serif" size="2"> = 12, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">j</font><font face="Times New Roman, Times, Serif" size="2"> = 8 (Computer waits for a third number)</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table></td></tr><tr><td valign="top"><font face="Times New Roman, Times, Serif" size="2">7. </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">cin聽>>聽i聽>>聽x;</font></td><td valign="top"><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">46聽32.4聽15</font></td><td valign="top"><table border="0" cellspacing="0" cellpadding="0"><tr><td rowspan="5"><img src="3e26ecb1b6ac508ae10a0e39d2fb98b2.gif" border="0" width="0" height="1" alt="3e26ecb1b6ac508ae10a0e39d2fb98b2.gif" /></td> <td colspan="3" height="1"></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">i</font><font face="Times New Roman, Times, Serif" size="2"> = 46, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="2">x</font><font face="Times New Roman, Times, Serif" size="2"> = 32.4 (15 is held for later input)</font></td><td></td></tr><tr><td colspan="3"></td></tr><tr><td colspan="3" height="1"></td></tr></table></td></tr></table></td></tr></table><br /></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_134.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_135</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_136.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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