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Computers store everything, from text to photos and music, as binary code: long strings of just two digits, 0 and 1. Each digit is a bit, and eight bits make a byte, which can take 256 different values, enough to stand for any letter on a keyboard.

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Computers use two digits because an electronic switch is easy to read reliably as either on or off, with current flowing or not; telling ten voltage levels apart would cause far more errors. The German philosopher and mathematician Gottfried Leibniz published an account of binary arithmetic in 1703. In 1937 Claude Shannon, then a master's student at MIT, showed that switching circuits could carry out logic, and his famous 1948 paper on information used the word 'bit', short for binary digit, which he credited to his colleague John Tukey. Whether a pattern of bits means a letter, the colour of a pixel or a sound depends on the agreed format: in the common ASCII code, for example, 01000001 is a capital A.

Türkçe oku
Bilgisayarlar metinden fotoğrafa ve müziğe kadar her şeyi ikili kodla, yani yalnızca 0 ve 1'den oluşan uzun dizilerle saklar. Bu rakamların her birine bit denir. Sekiz bit bir bayt eder; bir bayt 256 farklı değer alabilir, bu da klavyedeki her harfi göstermeye yeter.

Bilgisayarlar iki rakam kullanır, çünkü elektronik bir anahtarın açık mı kapalı mı olduğu, yani akımın geçip geçmediği kolayca ve güvenilir biçimde okunur; on ayrı gerilim düzeyini birbirinden ayırt etmek çok daha fazla hataya yol açardı. Alman filozof ve matematikçi Gottfried Leibniz, ikili aritmetiği 1703'te yayımladığı bir yazıda anlattı. 1937'de MIT'de yüksek lisans öğrencisi olan Claude Shannon, anahtarlı devrelerin mantık işlemleri yapabileceğini gösterdi. 1948'de yayımladığı ünlü bilgi kuramı makalesinde de “binary digit” (ikili rakam) sözünün kısaltması olan “bit” kelimesini kullandı ve kelimeyi meslektaşı John Tukey'e borçlu olduğunu belirtti. Bir bit dizisinin harf mi, piksel rengi mi, yoksa ses mi olduğu, hangi kurala göre okunduğuna bağlıdır. Örneğin yaygın ASCII kodunda 01000001, büyük A harfidir.

Sources and further reading

Background reading: Binary code
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