編譯器不計算長度×寬×高爲立方英寸

Question

我做一個比較簡單的程序來計算的長度×寬×高爲立方英寸。我應該得到一個像XXXXXXX.XX這樣的答案，但相反，編譯器給我0.000000

我沒有其他錯誤。我的主要問題是如何獲得數字來計算？

#include <stdio.h> 

double length; 
double width; 
double height; 

// This is the volume in cubic inches. 
double VolumeCubicInch; 

// This is the volume in cubic feet. 
double VolumeCubicFeet; 

int main() { 
    // Ask the user to enter the length width and height of a box (in inches). 

    // First print asks user to enter the length of a box in inches. 
    printf("Please enter the length of a box in inches.\n"); 
    // The user reads in the length number of the box in inches. 
    scanf("%lf", &length); 

    // Second print asks user for the width of the box in inches. 
    printf("Now please enter the width of the box in inches.\n"); 
    // The user reads in the width number in inches. 
    scanf("%lf", &width); 

    // Then the third print asks user for the height of the box in inches. 
    printf("Please enter the height of box in inches.\n"); 
    // The user reads in the height of the box in inches. 
    scanf("%lf", &height); 

    // Calculate the volume of the box, in cubic inches and output the result. 
    // Using a newly created variable called VolumeCubicInch, it will allow the  calculation 
    // of the box's volume to be calculated in cubic inches. 
    // Length output given: 15.8 
    // Width output given: 23.34 
    // Height output given: 75.345 
    VolumeCubicInch = length * width * height; 
    // The resulted volume in cubic inches will be outputted using a print statement. 
    // Output should be: The volume is XXXXXXX.XX cubic inches. 
    printf("The volume is %lf cubic inches.\n", &VolumeCubicInch); 

    // Calculate the volume in cubic feet, and output the result. 
    // Using the variable VolumeCubicFeet will produce the volume in cubic feet. 
    // VolumeCubicFeet = ; 
    // The value or result of the volume in cubic feet will be outputted using  the variable VolumeCubicFeet. 
    // The output should be: The volume is XXXX.XX cubic feet. 
    // printf("The volume is %lf cubic feet.\n", &VolumeCubicFeet); 

    // Note that a box that is 12 x 12 x 12 inches is 1.0 cubic feet. 
    // *Be sure that your program gets that answer.* 

    system("PAUSE"); 
    return 0; 
} 

Answer 1

您傳遞的結果，而不是它的價值地址：

printf("The volume is %lf cubic inches.\n", &VolumeCubicInch); 

而應該傳遞值，並指定2位小數：

printf("The volume is %.2f cubic inches.\n", VolumeCubicInch); 

注：

• 的l修改有必要scanf轉換爲double格式而不是float。 printf總是促進float值double，所以%f格式用於兩者，並且如果指定的l被忽略。
• 對於類型long double，您將在scanf和printf中使用%Lf轉換說明符。
• 您可以通過在%和f格式字符之間的小數點後傳遞精度字段來指定小數位數。

Answer 2

兩件事情：

1. scanf需要變量的地址是掃描，因爲它需要寫入這些變量。 printf不;它需要的參數的價值，因爲它只是讀/打印它們，因此該行：

   printf("The volume is %lf cubic inches.\n", &VolumeCubicInch); 
   

   應該僅僅是：

   printf("The volume is %lf cubic inches.\n", VolumeCubicInch); 
   

2. 爲了打印出「XXXXXXX。 XX」（即保留兩位小數），作爲你在意見欄內註明您的輸出，你可以使用%.2格式長度修改，如：

   printf("The volume is %.2f cubic inches.\n", VolumeCubicInch);