c - 一个简单的 c 程序的演练

Question

当这个程序运行时，我有这个问题要遍历并显示输出。我不明白的一件事是如何发现 f 是四甚至根本找不到。我知道正确的答案是

7 猎鹰 3

9 RK 4

_
我只是不知道他们是如何发现 f 值为 4 的，一旦我有了，我就可以做剩下的事了

#include <stdio.h> 
#include <string.h> 

void falcon(int f); 
char a[20]; 

int main() { 
    int i, j; 
    a[3] = 'G'; 
    a[1] = 'K'; 
    i = 3 + 2 * 3; 
    j = 4; 
    a[2] = 'Y'; 
    falcon(j); 
    printf("%d %s %d\n", i, a, j); 
} 

void falcon(int f) { 
    int j; 
    j = 11 % f; 
    printf("%d falcon %d\n", f+3, j); 
    a[2] = '\0'; 
    a[0] = 'R'; 
}

Answer 1

让我们一起来看看这个程序（去掉一些不相关的部分）。

#include <stdio.h> 
#include <string.h> 

void falcon(int f); 
char a[20]; 

int main() {
    int i, j;
    j = 4; 
    falcon(j); // in other words, falcon(4). Now, let's go down to the 
    // falcon function where the first argument is 4.
    printf("%d %s %d\n", i, a, j); 
} 

void falcon(int f) { // Except here we see that in this function,
                     // the first argument is referred to by 'f', 
                     // which, as we saw, is 4.
    int j; 
    j = 11 % f; // here, j is equal to the remainder of 11 divided by
                // f, which is 4.
    printf("%d falcon %d\n", f+3, j);
}

Answer 2

现在你明白了为什么代码不应该有is 和js 作为变量名，除非在循环中。

无论如何，

char a[20];顶部说这a是一个全局声明的字符数组。

int main()
{ 
   int i, j; // declares two local stack variables, i and j
   a[3] = 'G'; // sets 4th location in 'a'(remember, arrays start at 0) to 'G'{useless}
   a[1] = 'K'; // sets 2nd location in 'a' array to 'K'
   i = 3 + 2 * 3; // i is now 9 {remember, multiplication before addition}
   j = 4;    // j is now 4
   a[2] = 'Y';  // a[2] is now 'Y'
   falcon(j);  // call to falcon, with argument 4, explained next
   printf("%d %s %d\n", i, a, j);  // prints "9 RK 4"
   //return 0; -- this should be added as part of 'good' practices
} 



 void falcon(int f) 
 { 
     // from main(), the value of 'f' is 4
     int j;  // declares a local variable called 'j'
     j = 11 % f;  // j = 11 % 4 = 3 
     printf("%d falcon %d\n", f+3, j); // prints 7 falcon 3
     a[2] = '\0'; // a[2] contains null terminating character, overwrites 'Y'. 
     a[0] = 'R'; // sets a[0] to 'R'. At this moment, printf("%s",a); must yield "RK"
 }