Valid, albeit ancient, advice -- much like the XOR swap.

It's one of those things that language implementers knew about ages ago, and should be done by the compiler automagically (or it may take some optimization option).

Bottom line: don't do this unless your compiler sucks. Write code to multiply by 4 like this num*=4. Obfuscating it as num<<=2 will make your code look strangeto newbies, and it will look like a newbish hack to old timers (both making what you write a little suspect).

And don't forget that right-shifting signed values is implementation defined!