Windows-1256 is a code page used to write Arabic (and possibly some other languages that use Arabic script, like Persian and Urdu) under Microsoft Windows. This code page is not compatible with ISO 8859-6 and MacArabic encodings.
It encodes every abstract single letter of the basic Arabic alphabet, not every concrete visual form of isolated, initial, medial, final or ligatured letter shape variants (i.e. it encodes characters, not glyphs). The Arabic letters in the C0-FF range are in Arabic alphabetic order, but some Latin characters are interspersed among them. These are some Windows-1252 Latin characters used for French, since this European language has some historic relevance in former French colonies in North Africa such as Morocco and Algeria. This allowed French and Arabic text to be intermixed when using Windows 1256 without any need for code-page switching (however, upper-case letters with diacritics were not included).
Unicode is preferred over Windows 1256 in modern applications, especially on the Internet; meaning the dominant UTF-8 encoding for web pages (see also Arabic script in Unicode, for complete coverage, unlike for e.g. Windows 1256 or ISO-8859-6 that do not cover extras). Less than 0.1% of all web pages use Windows-1256 in September 2019.
Since the original code page left 9 values (bytes) marked as "NOT USED" in the original specification, these bytes were used later for additional characters needed for the Perso-Arabic script (for the Persian and Urdu languages), plus the euro sign.
The following table shows the extended version of Windows-1256. Each character is shown with its Unicode equivalent and its decimal code.
Here every Arabic letter is shown in isolated form. The actual forms of the letters inside Arabic words are rendered by a combination of software rules and appropriate font support.