C學習筆記（二）－理論

• 理論選擇易錯題

理論選擇易錯題

1. What is the output of this C code?

   #include <stdio.h>
   	int main(){
   	int i = j =10;
   	printf("%d\n", j++);
   	return 0;
   }
   

   Ans: Compilation error: Use of undeclared identifier ‘j’

2. What is the output of this C code?

   #include <stdio.h>
      int main(){
      int i =0, j =0;
      if(i &&(j = i +10)); //！！！
      		printf(“%d”,j);
      return 0;
   }
   

   Output: 0

3. What is the output of this C code?

   #include <stdio.h>
   int main(){
   	float x =0.1;
    	printf("%d, ", x);
   	printf("%f", x);
   	return 0;
   }
   

   Ans: Junk value, 0.100000

4. What is the output of this C code?

   #include <stdio.h>
   int main(){
     float x = 10;
     if (x < 5)
       printf("x < 5");
     else if (x > 10)
       printf("x > 10");
     else
       printf("Unknown");
   
     return 0;
   }
   

   Ans: Unknown

5. What is the output of the code given below?

   #include <stdio.h>
    
   
   int k = 0;
   void display(){
   	printf("%d ",k++);
   	//main裡的k未傳入
   }
   int main(){
   	int i;
   	static int k = 10;
   	for (i = 0; i < 5; i++)
   	display ();
   	printf("\n");
   	return 0;
   }
   

   Ans: 0 1 2 3 4

6. What is the output of this C code?

   #include <stdio.h>
   int main(){
   	extern int x;
   	int x = 0;
   	printf("%d",x);
   	return 0;
   }
   int x = 100;
   

   Ans: compile-time error: Non-extern declaration of ‘x’ follows extern declaration

7. Computer can execute the code in ____.
   Ans: machine language

8. ___ translates high-level language program into machine language program.
   Ans: A compiler(編譯程式)