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Fonts & Encodings by Yannis Haralambous

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3.4. Rendering properties

3.4.1. The Arabic and Syriac scripts

The characters of these scripts have two additional properties: joining type and joining group. To understand what these terms mean, let us recall the properties of these two scripts.

The scripts include three types of letters:

  • those that have four contextual forms: initial, medial, final, and isolated, the isolated form being both initial and final;

  • those that have two contextual forms: final and isolated;

  • those that have only one contextual form.

Let B be a letter with four forms and R a letter with two forms. Let us use 0, 1, 2, and 3 to represent the isolated, initial, medial, and final forms, respectively. Thus we have at our disposal the forms B0, B1, B2, B3, and also R0 and R3.

Contrary to what one might expect, contextual forms do not refer to words but to contiguous strings of letters. An initial letter may very well appear in the middle of a word; that will occur if the preceding letter is a final form. Thus we shall concern ourselves here with strings of letters.

Here are the three rules to follow in order to build up strings:

  1. start the string with an initial letter;

  2. within the string, continue with a medial letter, or, if the required letter has no medial form, use its final form, which will end the string;

  3. the last letter of the string must necessarily be a final form.

Let us take a few typical examples of words of three letters: BBB, BBR, BRB, RBB, BRR, RBR, RRB, RRR.

In the first of these words, the first ...

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