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Many thanks - that explains it very well....avoid these like the plague unless you know what you are doing I would say!!

'&&' and '||' are what's called "short-circuiting" logical operators. In the case of &&, if the first operand is false, then it doesn't bother evaluating the second operand, because the whole expression is certain to be false. In the case of ||, if the first operand is true, then it doesn't bother evaluating the second operand, because the whole expression is certain to be true. '&' and '|' can also be used as logical operators though it's more common for them to be used as bitwise operators. When they're used as logical operators, both operands are always evaluated. The only situation in which you'd want this is if the second operand had some side effect (if it was a method call, say), though normally this type of programming is best avoided.