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copied!<p>In programming language theory (and in computability theory) <strong>WHILE and FOR loops have different theoretical properties</strong>:</p> <ul> <li><strong>a WHILE loop may never terminate</strong> (the expression could just be TRUE)</li> <li>the finite number of times a FOR loop is to execute is supposed to be known before it starts executing. <strong>You're supposed to know that FOR loops always terminate.</strong></li> </ul> <p>The FOR loop present in C doesn't technically count as a FOR loop because you don't necessarily know how many times the loop will iterate before executing it. (i.e. you can hack the loop counter to run forever)</p> <p>The class of problems you can solve with WHILE loops is strictly more powerful than those you could have solved with the strict FOR loop found in Pascal. </p> <p><strong>Pascal is designed this way so that students have two different loop constructs with different computational properties</strong>. (If you implemented FOR the C-way, the FOR loop would just be an alternative syntax for while...)</p> <p><strong>In strictly theoretical terms, you shouldn't ever need to modify the counter within a for loop.</strong> If you could get away with it, you'd just have an alternative syntax for a WHILE loop.</p> <p>You can find out more about "while loop computability" and "for loop computability" in these CS lecture notes: <a href="http://www-compsci.swan.ac.uk/~csjvt/JVTTeaching/TPL.html" rel="noreferrer">http://www-compsci.swan.ac.uk/~csjvt/JVTTeaching/TPL.html</a></p> <p>Another such property btw is that the loopvariable is undefined after the for loop. This also makes optimization easier</p>

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