Symbian for Software Leaders: Principles of Successful Smartphone Development Projects

Chapter 16. Designing for efficiency

The original electronic organizers

The first Psion organizer went on sale in 1984. Psion marketed it as "the world's first practical pocket computer". For 1984, it had an impressive feature list:

• 8KB "Datapak" (solid-state disk) for permanent storage of information

• A flat file "data" application for storage of all sorts of information

• A powerful calculator

• 24-hour clock and calendar

• A sliding case to protect the keyboard

• 4KB XIP (execute-in-place) ROM, 2KB RAM as standard

• Battery life of six months on a single 9V PP3 battery

• Optional additional program packs and Datapaks. (The optional program packs included a finance program, whose first version was written by David Potter, Psion's chairman.)

This feature list compared favorably with the micro computers of the time, such as the Commodore VIC 20 or Sinclair Spectrum.

A ROM budget of 4KB and a RAM budget of 2KB concentrate the mind wonderfully.

Of course, later Psion devices contained more memory. But the requirement for the software development team to write lean-and-mean code persisted. All through my time at Psion, limitations of memory size were regularly in mind.

Psion's first SIBO (16-bit operating system) computer, the MC400 laptop computer, was intended to have 256KB ROM and 256KB RAM. It had four slots for solid-state disks for additional programs or storage. In view of the amount of code written, it was eventually decided to use up one of these slots by shipping an extra 128KB disk with every computer, ...