The shape of a character in its final display form can depend on its position in a word or its position relative to neighboring characters. Changing the shape of a character is called shaping or contextual analysis. For example, in English handwriting, letters can have different shapes in isolation or connected to other letters: the letter "r" appears differently at the beginning, in the middle, or at the end of a word. In English printing, however, character representation is unaffected by position--a character in isolation or connected to other letters is identically represented. For example, lowercase "a" is represented as "a"--either by itself, at the start, in the middle, or at the end of a word as in: a, all, lap, formula.)
Arabic uses a cursive script, connecting one character to another as in English handwriting. All characters are affected in many different ways by their context. Arabic characters can have up to four final display forms: initial, final, medial, or isolated. During input, the keystrokes are stored as basic code-point values. The Arabic language engine reads the code-point values and selects the appropriate final display form from the context. Ligatures and diacritics, however, must also be considered.
Only the basic shape of each character appears on an Arabic keyboard.