FutureStarr

A On Screen Calculator

# On Screen Calculator

A quick and easy calculator for any device.

### Basic

Photo: This is what calculators looked like in the 1970s. Note the very basic 8-digit green display (it's called a vacuum fluorescent display) and the relatively small number of mathematical functions (all you could really do was +, −, ×, ÷, square roots, and percentages). What you can't see from this photo is how thick and chunky this calculator was and how big its batteries were. Modern calculators are far more advanced, much cheaper, and use a fraction as much battery power.

Now if you put different logic gates together, you can make more complex circuits called adders. You feed into these circuits two binary numbers as their input and get out a third, binary number as your output. The number that comes out is the binary sum of the numbers you put in. So if you fed in the electrical signals 10 and 11 you would get out 101 (2 + 3 = 5). The basic ingredient of adder circuits is a pair of logic gates, working in parallel, called a half adder, which can do sums no more complex than (wait for it!) 1 + 1 = 2. One example of a half adder looks like this: (Source: www.explainthatstuff.com)

### Use

Photo: This is what calculators looked like in the 1970s. Note the very basic 8-digit green display (it's called a vacuum fluorescent display) and the relatively small number of mathematical functions (all you could really do was +, −, ×, ÷, square roots, and percentages). What you can't see from this photo is how thick and chunky this calculator was and how big its batteries were. Modern calculators are far more advanced, much cheaper, and use a fraction as much battery power.

You're probably used to the idea that your computer screen makes letters and numbers using a tiny grid of dots called pixels. Early computers used just a few pixels and looked very dotty and grainy, but a modern LCD screen uses millions of pixels and is almost as clear and sharp as a printed book. Calculators, however, remain stuck in the dark ages—or the early 1970s, to be precise. Look closely at the digits on a calculator and you'll see each one is made from a different pattern of seven bars or segments. The processor chip knows it can display any of the numbers 0–9 by activating a different combination of these seven segments. It can't easily display letters, though some scientific calculators (more advanced electronic calculators with lots of built into mathematical and scientific formulae) do have a go. (Source: www.explainthatstuff.com)

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