if...else statement

1. 流程圖
   
   
   
2. 語法

   if(boolean_expression)
   {
      /* statement(s) will execute if the boolean expression is true */
   }
   else
   {
     /* statement(s) will execute if the boolean expression is false */
   }
   

3. 範例

   [dywang@dyw219 zzz]$ vim if2.c 
   [dywang@dyw219 zzz]$ cat if2.c
   #include <stdio.h>
   
   main() {
       int a;
   
       printf("Enter an integer: ");
       scanf("%d", &a);
   
       if ( a>10 ) {
   		printf("%d > 10\n", a);
   	}
       else {
   		printf("%d <= 10\n", a);
   	}
       printf("a = %d\n", a );
   }
   

4. 編譯成功

   [dywang@dyw219 zzz]$ gcc -o if2 if2.c
   

5. 執行結果一

   [dywang@dyw219 zzz]$ ./if2
   Enter an integer: 7 
   7 <= 10
   a = 7
   

6. 執行結果二

   [dywang@dyw219 zzz]$ ./if2
   Enter an integer: 19
   19 > 10
   a = 19