Infinite loop

**Ditrik** · 01-11-2010

I stumbled upon a problem while I was coding.

Code:

void main()
{
	int n;
	do
	{
		printf("Write a number in interval [10,100]\n");
		scanf("%d",&n);
	}while(n<10 || n>100);
}

This works just fine when I enter a number, but when I enter a char for example "A", it just starts repeating "Write a number in interval [10,100]\n" infinitely. I tried to explain this to myself but I just couldn't come to a logical conclusion.

In my opinion n should be initialized with 65 and program should leave the loop and end.

**Salem** · 01-11-2010

A isn't a number.
The next time around the loop, A still isn't a number.
The next time around the loop, A still isn't a number.
The next time around the loop, A still isn't a number.

Unless you do something to fix that, you're going nowhere.

Try using fgets() to read a whole line, then using say sscanf to parse it.
See the FAQ.

**bithub** · 01-11-2010

When you enter "A", scanf fails and n is not assigned any value. That is why the loop goes forever. Check the return value of scanf() to see if 'n' was successfully given a value.

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