Spelling is the writing of one or more words with letters and diacritics. In addition, the term often, but not always, means an accepted standard spelling or the process of naming the letters. In the sense of a standard, spelling is one of the elements of orthography and a prescriptive element of alphabetic languages. Spellings attempt to transcribe the sounds of the language into alphabetic letters, but phonetic spellings are exceptions in many languages for various reasons.
As English is the most common language of science, literature and media around the globe, there are several spelling and writing style guides published for this language. AP Style Guide, The New York Times Style Guide, APA, MLA and Oxford Style are among the most established guidelines for spelling.
Microsoft Office has been a pioneer in spell checking and saved huge time and effort for billions of people. Today, new content management tools have built-in modules to check spelling in multiple languages.
Localization companies use CAT tools which also feature automated spell checks. Good localization engineers add regular expressions to better manage spelling.