Tally marks, or hash marks, are a unary numeral system

Unary numeral system

The unary numeral system is the bijective base-1 numeral system. It is the simplest numeral system to represent natural numbers: in order to represent a number N, an arbitrarily chosen symbol representing 1 is repeated N times. For example, using the symbol | , the number 6 is represented as ||||||...

. They are a form of numeral

Numeral system

A numeral system is a writing system for expressing numbers, that is a mathematical notation for representing numbers of a given set, using graphemes or symbols in a consistent manner....

 used for counting

Counting

Counting is the action of finding the number of elements of a finite set of objects. The traditional way of counting consists of continually increasing a counter by a unit for every element of the set, in some order, while marking those elements to avoid visiting the same element more than once,...

. They allow updating written intermediate results without erasing or discarding anything written down. However, because of the length of large numbers, tallies are not commonly used for static text.

In Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, tally marks are most commonly written as groups of five lines. The first four lines are vertical, and every fifth line runs diagonally or horizontally across the previous four vertical lines, in either of the two possible directions (the popular direction may vary from region to region).