The for statement implements an iterative loop and requires you to specify the number of iterations. The syntax of the for statement is:

for counter := initial_value to final_value do statement_list
// or
for counter := initial_value downto final_value do statement_list

counter is a variable which increments (or decrements if you use downto) with each iteration of the loop. Before the first iteration, counter is set to initial_value and will increment (or decrement) until it reaches final_value. final_value will be recalculated each time the loop is reentered.
This way number of loop iterations can be changed inside the loop by changing final_value. With each iteration, statement_list will be executed.

initial_value and final_value should be expressions compatible with counter.

If final_value is a complex expression whose value can not be calculated in compile time and number of loop iterations is not to be changed inside the loop by the means of final_value, it should be calculated outside the for statement and result should be passed as for statement's final_value. statement_list is a list of statements that do not change the value of counter. If statement_list contains more than one statement, statements must be enclosed within begin-end block.

Here is an example of calculating scalar product of two vectors, a and b, of length 10, using the for statement:

s := 0;
for i := 0 to 9 do 
  s := s + a[i] * b[i];

Endless Loop

The for statement results in an endless loop if final_value equals or exceeds the range of the counter’s type.

More legible way to create an endless loop in Pascal is to use the statement while TRUE do.

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