What were the specific challenges you faced in the implementation of Search-As-You-Type algorithm?

Autodispens was written in DOS before the Window’s operation system was established. Implementing Search-As-You-Type in DOS was difficult since one can only use sequential programming because DOS is not a multitasking operation system. In-order to have a workable ‘real time’ program in DOS it was necessary to monitor and process each key press while a particular procedure was being carried out. That was not practical in the normal style of programming.

The first PC used had only 20 megabytes hard disk capacity and less than 1 megabyte of RAM. The speed of the CPU was 20 mega hertz! Within those narrow limits of RAM and the CPU speed it was a difficult task to get a workable Search-As-You-Type system. When accessing the hard drive a specific section of the hard drive was block read and put into RAM. The array of data was processed by a series of procedures and functions which consisted of string manipulations and string comparisons. The list was shortlisted using an array of pointers or numbers without altering the original array of data in memory.


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