C语言笔记

た入场券 2022-08-05 02:53 162阅读 0赞

1. 1. 数组名不能进行自增、自减运算
 
 指针可以进行自增、自减运算
 
 Define
 
 \#definef(x) x+2
 
 表示将语句中所有形如f(x)的文字替换为x+2的形式的文字。
 
 即
 
 i=f(a)/f(b)
 
 被替换为
 
 i=a+2/b+2
 
 根据前面变量的定义a=4b=2
 
 i=4+2/2+2=4+1+2=7
2. 标识符
 
 C语言的合法标识符由字母、下划线、数字这三个方面组成，但开头必须是字母或下划线。
 
 另外，关键字不能是标识符，如main，int等。
 
 
 
3. 变量声明与赋值
 
 <table style="direction:ltr; border-collapse:collapse; border-style:solid; border-color:#A3A3A3; border-width:1pt; margin-left:.7083in"> 
 <tbody> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> 表达式 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 正确与否 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> 说明 </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char *a="china"; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 正确 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char*a; *a="china"； </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 错误 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char*a; a="china"; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 正确 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char a[6]={"china"}; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 正确 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char a[]={"china"}; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 正确 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char a[4]="abc",b[4]="abc"; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 正确 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char b[4];char&nbsp; a[4]=b[4]="abc"; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 错误 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char a[4]=b[4]="abc"; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 错误 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> 编译器会提示你b未定义 </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.9138in; padding:4pt 4pt 4pt 4pt"> char b; char a=b='d'; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.3805in; padding:4pt 4pt 4pt 4pt"> 正确 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:2.3152in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 </tr> 
 </tbody> 
 </table>
 
 
 
4. 数组名不能进行自增、自减运算
 
 指针可以进行自增、自减运算