Study day 8

C language

1. The general form of the for statement

   1. For — loop structure

   2. for（ ：）

   3. int a, sum = 0;
      for (a = 1; a <= 100; a++)
      {
      	sum = sum + a;
      }
      printf("sum=%d", sum);

   4. A = 1 in parentheses is the initial value of the cyclic variable, a < = 100 is the condition for the end of the cyclic variable, a + + is the added value of the cyclic variable

   5. The expression is 1, which can be omitted

   6. int a, sum = 0;
      a = 1;// You can assign a value to it first - the same usage as the previous one
      For (; a < = 100; a + +) // must have; If there is no sign, it will fail. It is only to omit expression 1, that is, a = 1
      {
      	sum = sum + a;
      }
      printf("sum=%d", sum);

   7. Expression 2 can also be omitted, but the end of break must be added, otherwise it will loop indefinitely

   8. int a, sum = 0;
      a = 1;
      For (;; a + +) // must have; If no, it will fail
      {
      	sum = sum + a;
      	If (a > = 100) // conditions for ending the loop
      		break;  // The purpose is to end the cycle
      
      }
      printf("sum=%d", sum);

   9. Effect omitted from expression 3

   10. int a, sum;
       
       for (sum = 0,a = 1; a <= 100; )// Must have; If no, it will fail
       {
       sum = sum + a;
       	
       	a++;// Omit expression 3 to ensure that the for loop can end normally
           
       
       }
       printf("sum=%d", sum);

   11. sum = 0,a = 1;

       1. Sum = 0, - comma expression
                 	2. sum = 0,a = 1; —— Expression 1. There is a comma expression in expression 1

   12. Expression 1, expression 2 and expression 3 in for can be omitted

2. For statement actual

3. Main description of the for statement

4. 、