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A program can stop working even if nobody changes a line of it, because the computers, operating systems and online services it relies on keep changing. Programmers call this software rot, or bit rot.

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The name is a joke: the bits do not really decay, though it can look that way. A classic case is old computer games that used the speed of the processor as their clock, so on faster computers they ran too fast to play. Online features fail when the company switches off its server. Secure websites rely on digital certificates, electronic proofs of identity that have expiry dates, so an old phone or computer that no longer gets updates slowly loses the ability to open them. In March 2021 the older versions of TLS, the security standard that encrypts web connections, were officially retired, cutting off many old browsers. Programs also rely on ready-made building blocks written by others, called libraries; when a library changes or disappears, the program can break. This is why software needs regular maintenance, and why archives run old programs in emulators, which imitate old machines.

Türkçe oku
Bir program, tek satırına dokunulmasa bile bir gün çalışmayı bırakabilir; çünkü dayandığı bilgisayarlar, işletim sistemleri ve çevrimiçi hizmetler değişmeye devam eder. Yazılımcılar buna yazılım çürümesi ya da “bit rot” der.

Ad bir şakadır: Programın bitleri gerçekten çürümez, ama durum öyleymiş gibi görünür. Klasik bir örnek, işlemcinin hızını saat olarak kullanan eski bilgisayar oyunlarıdır; bu oyunlar daha hızlı bilgisayarlarda oynanamayacak kadar hızlı akar. Şirket sunucusunu kapatınca çevrimiçi özellikler çalışmaz olur. Güvenli web siteleri, son kullanma tarihi olan dijital sertifikalara, yani elektronik kimlik belgelerine dayanır; güncelleme almayan eski bir telefon ya da bilgisayar bu yüzden zamanla bu siteleri açamaz hâle gelir. Web bağlantılarını şifreleyen güvenlik standardı TLS'nin eski sürümleri Mart 2021'de resmen emekliye ayrıldı ve pek çok eski tarayıcı devre dışı kaldı. Programlar, başkalarının yazdığı ve kütüphane denen hazır parçalara da dayanır; bir kütüphane değişince ya da ortadan kalkınca program bozulabilir. Yazılımın düzenli bakıma ihtiyaç duymasının ve arşivlerin eski programları, eski makineleri taklit eden öykünücü (emülatör) yazılımlarla çalıştırmasının nedeni budur.

Sources and further reading

Background reading: Software rot
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