Each part of the header can have multiple statements separated by commas.
Header examples:
for ( i = 0; i < 10; i ++ ) { ... }
//standart header
for ( i = 0, x = 1.; i < 10; i += 2, x *= 0.1 ){ ... }
//in this case, we use two variables that will change after the execution of the loop body - these are the variables i and x
// variable i changes in increments of 2: i + = 2 - abbreviated notation from i = i + 2
// variable x with each step increases by 0.1 times x = x * 0.1 - abbreviated x * = 0.1