Slabacus (ver 2.0.0) Abandoned Freeware Slabacus is two programs, a Slide Rule and an Abacus. While the need for an Abacus is debatable, there are often times where a Slide Rule is very helpful. It is easier to make approximations and empirically work out formulas when you can easily see what number values fall around the numbers you are working with. A Slide rule also allows you to work backwards to derive a formula from the answer (something extremely tedious to accomplish with a digital calculator). An example of how an electrician would find a slide rule useful, is if you are working with setting Wattages. If you are adjusting wattages by setting a separate Volt and Amp meter, the slide rule will let you work backwords from the answer (the wattage you seek), and let you easlily infer the best settings for the Volt and Amp meters to achieve it (I.e., if you seek 20 watts, setting the meters to 2 and 10 would work, but setting them to 4 and 5 might be better).