Books and web pages frequently include tables of the four different versions of each letter of the Arabic alphabet, initial, final, medial, and isolated. This does not do justice to the Naksh script; although it is not as different from the Latin script in its requirements as Nastaliq, some features of even this script were discarded to allow Western typesetting equipment to be used for Arabic.
In a discussion some time ago on Typophile, I mentioned that on a typewriter, the four forms of Arabic letters are reduced to two, since the line joining two letters can be associated with the first letter in its entirety. This is because kerning is no problem with a typewriter, and letters can overprint each other, unlike the case with metal type.
I have now found more information about this. It turns out that the reduction of the letters of the Arabic alphabet to two basic forms for a typewriter was described in U.S. Patent 637,109, issued to Selim Haddad of Cairo, Egypt, then in the Turkish Empire, on November 14, 1899.