What are the three actons a counter variable uses?

Answer 1

Variables don't have any "actions". A variable provides storage for a value, nothing more. A counter variable is typically used in a bounded for loop. A for loop has three clauses, each of which is optional. The first clause is the initialiser which can be used to initialise a control variable upon entry to a bounded loop. The second clause is the conditional expression which is evaluated at the start of each iteration. If that expression evaluates false, execution passes to the statement following the for statement, otherwise the body of the loop executes. The second clause is typically used to test the control variable is within the bounds of a bounded loop. The third clause is an operation that will be performed at the end of each iteration. In a bounded loop, this clause is typically used to increment the control variable. For example:

for (int x=0; x<10; ++x) {

/* ... */

}

The above loop is a bounded loop that will execute the body of the loop 10 times. The control variable, x is first initialised to 0. At the start of each iteration, if x<10 is true, the body of the loop will execute one iteration. At the end of each iteration, the ++x statement increments x. When x is 10, the x<10 expression becomes false and execution passes to the statement immediately after the for loop.