[Study Notes] [C Language] cyclic structure-for, learning note structure-

[Study Notes] [C Language] cyclic structure-for, learning note structure-
1. Use:

For (Statement 1; condition; Statement 2)
{
Loop body
}

Statement 1: initialization statement
Statement 2: Incremental statement (statement executed after the loop body is executed)

1. The for statement is executed once at the beginning. 1 (the entire for loop is executed only once)
2. Determine whether the condition is true. If the condition is true, a loop body is executed, Statement 2 is executed, and the condition is true again.

2. Note

Do not enter a semicolon after ().
For (int I = 0; I <5; I ++ );
{
Printf ("Haha \ n ");
}

Error: the scope of variable a is not clear.
To define a new variable in the loop body, you must wrap it in braces {}.
For (int I = 0; I <5; I ++)

Int a = 10;


Error
For (int I = 0; I <10; I ++, a ++)
{
// A can only be used in loop body {}
Int a = 10;
}

Int a = 10;

For (int I = 0, a = 9; I <5; I ++)
{
// Int I = 10;
Int a = 11;

Printf ("a = % d \ n", );
}

The simplest use of the for loop to achieve an endless loop
For (;;);

 

3. nested loop exercises

1/* 2 friend list 1 3 friend 1 4 friend 2 5 friend list 2 6 friend 1 7 friend 2 8 friend list 3 9 friend 110 friend 211 */12 13 # include <stdio. h> 14 int main () 15 {16 17 for (int I = 1; I <= 4; I ++) 18 {19 // printf ("friend list % d \ n", I + 1); 20 printf ("friend list % d \ n", I ); 21 22/* 23 printf ("friend 1 \ n"); 24 printf ("friend 2 \ n"); 25 printf ("friend 3 \ n "); 26 printf ("friend 4 \ n"); 27 printf ("friend 5 \ n"); */28 29 for (int j = 1; j <= 7; j ++) 30 {31 printf ("friend % d \ n", j); 32} 33} 34 35 return 0; 36

1/* 2 prompt the user to enter a positive integer n. If n = 5, the following figure is output, other n values and so on 3 ******* 4 ****** 5 ***** 6 **** 7*8 */9 10 # include <stdio. h> 11 12 int main () 13 {14 // 1. define a variable to store the user input value 15 int n = 0; // You must initialize 16 17 // 2. judging n value combination unreasonable 18 while (n <= 0) 19 {20 // 2.1 prompt the user to enter a positive integer 21 printf ("Please enter a positive integer: \ n "); 22 23 // 2.2 receive input data 24 scanf ("% d", & n); 25} 26 27 // 3. output graph 28 for (int I = 0; I <n; I ++) // number of rows: 29 {30 // printf ("***** \ n"); 31 for (int j = 0; j <n-I; j ++) 32 {// The number of 33 printf ("*"); 34} 35 36 printf ("\ n"); 37} 38 39 return 0; 40}