Learn how computers perform mathematical operations. DIY Calculator is based on a very simple microcomputer system comprising a central processing unit (CPU), some memory, and some input and output (I/O) ports (these ports allow the system to "talk" with the outside world). The CPU itself is very straightforward and easy to understand: it has an 8-bit data bus and a 16-bit address bus; it contains a small number of simple registers like an accumulator, index register, and stack pointer; and it supports a very simple instruction set along the lines of ADD, SUBTRACT, SHIFT, ROTATE, AND, and OR.

Now, here's the clever part. Instead of implementing our microcomputer system as a real (physical) board, we created it as a "virtual machine" that runs on a standard personal computer (an IBM-compatible PC running Windows 2000 or Windows XP). This virtual system comes equipped with an assembler and a variety of diagnostic tools, such as a CPU Register Display, a Memory Display, and .... the list goes on.

The DIY Calculator also features a virtual calculator front panel with buttons, lights, and a pseudo-liquid crystal display (LCD) as shown below. This front panel is "connected" to the virtual computer via its input and output ports.

The license of this software is Freeware, you can free download and free use this calculator software.