How do you break the infinite loop program in turbo c plus plus without break key?

Answer 1

In short, you don't. By definition, an infinite loop is one that has no exit condition. For example:

while( 1 );

When execution reaches this line, the program will get no further. It will continually execute this same line of code because the only way for this loop to exit is when the literal constant 1 becomes the literal constant 0 -- which would clearly be impossible.

By the same token, the following lines are also infinite loops:

do while( 1 );

for(;;);

Infinite loops of this kind are completely useless in production code. Apart from the fact they do nothing remotely useful, an infinite loop renders the program completely invalid. And yet we hear the term infinite loop being used in code all the time.

The truth is that while we do use the term infinite loop, it is not strictly infinite. What we really mean is that although the loop statement needn't have an exit condition, the body of the loop does!

By way of an example, consider the following infinite loop:

while( 1 )

{

if( !rand() )

break;

}

Here, the loop statement is clearly infinite, but the body contains the all-important exit condition. In this case, the loop continually produces random numbers in the range 0 to 32767. If the number is zero, then control passes to the break statement at which point the loop ends and execution continues at the statement following the closing brace of the loop. Thus on every loop there's a 1 in 32768 chance the loop will end. There's a remote possibility the loop may never end however it's highly unlikely. Note that in its current form, the random numbers will produce the same sequence over an over and the loop will therefore execute the same number of times every time the program is run. But even if we seed the random numbers to produce a different sequence each time, the loop will exit after just a few seconds at most. The odds of never ever producing a zero are remote in the extreme.

So that's the so-called infinite loop -- which is not really infinite after all. But to answer the question, we break out of an infinite loop by providing at least one exit condition within the body of the loop. If the program is to be run within an event-driven environment (such as Windows), we might periodically test the message queue to see if a specific key sequence is pending (such as ESC) and prompt the user to save the current state of the loop so that it can continue at a later date before gracefully exiting the loop. By the same token, we should also check for a program exit message (perhaps the user clicked the close window button, or even chose to shutdown Windows in the middle of the loop) and we must cater for those eventualities too.

Ultimately, how you exit an infinite loop will depend entirely upon the purpose of the loop. There is no one-size-fits-all solution. But there must be at least one exit condition that must logically fire at some point in time. If not, the loop is truly infinite and will completely invalidate your program.