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  • <C Primer Plus >1 Constants and the C Preprocessor

     1 #include <stdio.h>
     2 #define    PI 3.14159
     3 int main(void){
     4     float area, circum, radius;
     5 
     6     printf("What is the radius of your pizza>
    ");
     7     scanf("%f", &radius);
     8     area = PI * radius *
     radius;
     9     circum = 2 * PI *radius;
    10     printf("Your pizza parameters are as follows:
    ");
    11     printf("Circumference = %1.2f, area = %1.2f 
    ", circum, area);
    12     getchar();
    13     return 0;
    14 }

    The #define statement can be used for character and string constants,too . The following example are valid:

    1 #define BEEP 'a'
    2 #define TEE 'T'
    3 #define ESC '33'
    4 #define OOPS "Now you have done it!"

    Remember:
    1 It is a sensible C tradition to type constants in uppercase.
    2 Don't make the common error when using the #define.
    3 The const Modifier makes variables read-only ;you cannot alter the value of the variables.
    4 C has a third way to create symbolic constants,and that is the enum.
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  • 原文地址:https://www.cnblogs.com/michael2016/p/6580050.html
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