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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_43</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_42.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_43</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_44.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 43</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">Every C++ program must have a function named </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">main</font><font face="Times New Roman, Times, Serif" size="3">. Execution of the program always begins with the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">main</font><font face="Times New Roman, Times, Serif" size="3"> function. You can think of </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">main</font><font face="Times New Roman, Times, Serif" size="3"> as the master and the other functions as the servants. When </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">main</font><font face="Times New Roman, Times, Serif" size="3"> wants the function </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Square</font><font face="Times New Roman, Times, Serif" size="3">. to perform a task, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">main</font><font face="Times New Roman, Times, Serif" size="3"> <i>Calls</i> (or <i>invokes)</i> </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Square</font><font face="Times New Roman, Times, Serif" size="3">. When the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Square</font><font face="Times New Roman, Times, Serif" size="3"> function completes execution of its statements, it obediently returns control to the master, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">main</font><font face="Times New Roman, Times, Serif" size="3">, so the master can continue executing.</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">Let's look at an example of a C++ program with three functions: </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">main</font><font face="Times New Roman, Times, Serif" size="3">, </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Square</font><font face="Times New Roman, Times, Serif" size="3">, and </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">Cube</font><font face="Times New Roman, Times, Serif" size="3">. Don't be too concerned with the details in the programjust observe its overall look and structure.</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">#include聽<iostream.h><br /><br />int聽Square(聽int聽);<br />int聽Cube聽(聽int聽);<br /><br />int聽main()<br />{<br />聽聽聽聽cout聽<聽"The聽square聽of聽27聽is聽"聽<聽Square(27)聽<聽endl;<br />聽聽聽聽cout聽<聽"and聽the聽cube聽of聽27聽is聽"聽<聽Cube(27)聽<聽endl;<br />聽聽聽聽return聽0;<br />}<br /><br />int聽Square(聽int聽n聽)<br />{<br />聽聽聽聽return聽n聽*聽n;<br />}<br /><br />int聽Cube(聽int聽n聽)<br />{<br />聽聽聽聽return聽n聽*聽n聽*聽n;<br />}</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">In each of the three functions, the left brace ( { ) and right brace ( } ) mark the beginning and end of the statements to be executed. Statements appearing between the braces are known as the <i>body</i> of the function.</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">Execution of a program always begins with the first statement of the </font><font face="Courier New, Courier, Mono New, Courier, Mono" size="3">main</font><font face="Times New Roman, Times, Serif" size="3"> function. In our program, the first statement is</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">cout聽<聽"The聽square聽of聽27聽is聽"聽<聽Square(27)聽<聽endl;</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">This is an output statement that causes information to be printed on the computer's display screen. You will learn how to construct output statements like this later in the chapter. Briefly, this statement prints two items. The first is the message</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_42.html">< previous page</a></td> <td align="center" width="40%" style="background: #EEF3E2"><strong style="color: #2F4F4F; font-size: 120%;">page_43</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_44.html">next page ></a></td> </tr> </table> </body> </html>⌨️ 快捷键说明
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