Language:
Portable mechanical aids are portable computing as a forerunner of today's pocket calculator, it probably already almost since humans began to deal with numbers, first for addition and subtraction are used mostly in the retail sector. Probably the most famous example is perform the abacus, a millennia-old computational tools, the origin and age was never clearly established, but which is still widely used worldwide and is still used even today in some regions of the Third World. It is a simple calculation tool for adding and subtracting the mechanical structure consists of a frame, are used in the sliding rods, each with 9 balls. The first line of the exhibit are the One, the second ten, etc. Later there were a variety of scientific and technical developments and purposes, some of which had a straightforward mechanical construction, but partly also waited upon with a rather complicated mechanical movements. The latest developments were for example the mechanical Curta or the slide rule, which were still in the last century, at least until the proliferation of electronic, scientific calculators, the leading computational help.