nested if statements

1. 語法

   if( boolean_expression 1)
   {
      /* Executes when the boolean expression 1 is true */
      if(boolean_expression 2)
      {
         /* Executes when the boolean expression 2 is true */
      }
   }
   

2. 範例

   [dywang@dyw219 zzz]$ cat if3.c 
   #include <stdio.h>
   
   main() {
       int a;
   
       printf("Enter an integer: ");
       scanf("%d", &a);
   
       if ( a>10 ) {
   		printf("%d > 10\n", a);
   		if ( a<100) {
   			printf("%d < 100\n", a);
   		}	
   	}
       else {
   		printf("a <= %d\n", a);
   	}
       printf("a = %d\n", a );
   }
   

3. 編譯成功

   [dywang@dyw219 zzz]$ gcc -o if3 if3.c
   

4. 執行結果一

   [dywang@dyw219 zzz]$ ./if3
   Enter an integer: 5
   a <= 5
   a = 5
   

5. 執行結果二

   [dywang@dyw219 zzz]$ ./if3
   Enter an integer: 49
   49 > 10
   49 < 100
   a = 49
   

6. 執行結果三

   [dywang@dyw219 zzz]$ ./if3
   Enter an integer: 200
   200 > 10
   a = 200