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### Arabic numerals

Decimal numbers are written (almost) everywhere in the world with Hindu-Arabic numerals. We use the notation

 0 1 2 3 4 5 6 7 8 9

what in the current arabic writing looks like

 ٠ ١ ٢ ٣ ٤ ٥ ٦ ٧ ٨ ٩

and that shows some resemblance.

##### Notations

In Germany you write a 1 always as (or even worse) where we would take it for a 7. In the Netherlands they write an 8 as 8 and we see this as the letter B.

##### Attention for 0 and 1

You would expect that all of the 10 digits can be handled in the same way. But that is not the case.

The digits 0 and 1 have special meanings, and when using them in calculations you must pay special attention. In primary school you may have noticed this already. The multipiclation table for 0 was excluded, because every number multiplied by 0 gives 0. It disappears. The table for 1 was easy, as every number multiplied by 1 stays unchanged. But that is just amazing.

A computer uses internally only zeroes and ones, so works binary. It is all about the opposites, like: on and off, black and white, light and dark, thing or nothing, one or none, etc. It are both very important numbers. So keep in mind

and