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The Psion Organiser was the brand name of a range of pocket computer developed by the British company Psion in the 1980s. The Organiser I (launched in 1984) and Organiser II (launched in 1986) had a characteristic hard plastic sliding cover protecting a 6x6 keyboard with letters arranged alphabetically.
The Organiser II can be considered the first usable PDA in that it combined an electronic diary and searchable address database in a small, portable device.
Production of consumer hand-held devices by Psion has now ceased; the company, after corporate changes, now concentrates on hardware and software for industrial and commercial data collection applications.
On an episode of The Gadget Show (first aired on 30 March 2009), the Psion was pitted against the BlackBerry for a place on the show's Hall of Fame. Whilst the Psion was highly praised as a device that pioneered portable computing, the accolade was ultimately given (by host Jon Bentley) to the BlackBerry.
 Organiser I
The Psion Organiser I model, launched in 1984 was the "World's First Practical Pocket Computer". Based on an 8-bit Hitachi 6301-family processor, running at 0.9MHz, with 4kB of ROM and 2kB of static RAM, and had a single-row monochrome LCD screen. The size in mm with the case closed is 142 x 78 x 29.3, and the weight is 225 grams.
The machine provided a simple flat-file database, calculator and clock, and had no operating system. The Organiser I supported removable storage write-once devices which used EPROM storage. The machine could host two of these so-called DATAPAKs (or simply PAKs), to which it could write data but which needed to be removed from the machine and erased by being exposed to ultraviolet light before they could be re-used. As Psion had patented the use of EPROMS as storage device it was impossible for other device manufacturers to copy this innovative approach to mobile storage.
Software supplied on DATAPAK included a crude programming language called POPL, in which end-users could write their own programs. Software DATAPAKs titled Science, Maths and Finance contained the POPL programming language editor, interpreter and runtime and extended the built-in calculator by adding named functions. These DATAPAKs also contained different sets of application programs written in the POPL language.
A far more sophisticated programming tool was later made available with the implementation of the Forth programming language, but was available to registered professional developers rather than end users. The Psion Forth Development System for the Organiser I was a powerful set of IBM PC-based cross-development tools for producing Forth application programs, including a Forth compiler. The Forth system on the Organiser I itself had a compiler to intermediate code, interpreter and runtime, and had a number of unusual design features one being that it could interpret - that is, read and execute - Forth intermediate code directly in place on a DATAPAK, rather than needing to copy it into precious RAM first, despite the DATAPAKs not being execute-in-place memory-mapped.
Software developed by Psion as part of the Organiser I project and application software after its launch was written in 6301 assembler language, in POPL, and in other custom-designed languages. Assembler language development at Psion itself was carried out using cross-development tools, including a cross assembler and linker, all of which ran on a DEC VAX.
Application developers writing in 6301 assembler struggled with the small amount of RAM (2k), and the lack of an operating system. Another difficulty for developers was with the performance limitations of the earliest DATAPAKs which used a serial-access internal architecture, as opposed to random access. Retrieving for example byte 2000 from a DATAPAK meant issuing successive hardware commands to either step from the current read position one address place at time until position 2000 was reached or in the worst case resetting the read position to zero and then issuing a step-forward command 2000 times.
The Hitachi 6301 processor is an enhanced development based on the Motorola 6801 implemented in CMOS, with a number of extra instructions, various hardware system-on-single chip facilities on-chip, power management and support for a sleep state. The particular variant chosen also had 4KiB of masked ROM on-chip, so an external ROM was not needed on the board.
Having fully static RAM and a processor whose clock could be frozen without losing state meant spectacular battery life, measured in weeks or even months. Minimal battery consumption was aided by the processor being frozen whenever there was no work to do, plus a deeper sleep mode which turned off the display.
The machine lacked a full independently battery-backed, date-time real-time hardware clock, instead it had a simple hardware counter. While the machine was sleeping, the counter counted 1024 seconds and then woke the machine very briefly so that software could add 1024 seconds to a record of the time held in RAM. This meant that when sleeping the machine woke very, very fleetingly every 17m 4s.
The original 1984 price was £99 (GBP) and $199 (CAD) and included one Datapak and one software DATAPAK, the "Utility" pack. This latter adds scientific and trigonometric functions to the otherwise basic calculator routines.
 Organiser II
In 1986, the successful Organiser II introduced a number of hardware improvements, a better keyboard and display, a much larger ROM and either 8K or 16K of battery-backed RAM, and featured a capable newly-designed single-tasking operating system. The first Organiser II models featured a two-line display. The new model supported a number of different types of improved DATAPAKs containing either EPROM or battery-backed RAM storage each storing between 8k and 128k of data. Later flashpaks (EEPROM) and RAMpaks were added to the range, capable of storing up to 256k on each extension slot.
The machine had vastly more application functionality, including a number of built-in application programs, an easy to use database, a diary and an alarm clock and featured end-user programmability in the form of the successful Organiser Programming Language (OPL), a BASIC-like language which was compiled to intermediate code, in contrast to the interpreters which were commonly available for other consumer computers of the time. More advanced users could reach into the system machine code routines either via direct machine code, or via calls from OPL, and could manipulate the built-in address database as well as create their own.
The Organiser II was widely used for commercial applications in companies such as Marks and Spencer, where it was used on the shop floor, and in the world's first large scale application of mobile technology in government where over 3000 were used for benefit calculations by the Employment Services department of the UK government.
The Organiser II also had an external device slot into which various plug-in modules could be fitted, including a device which provided an RS232 port (called 'CommsLink') thus enabling it to communicate with other devices or computers. This "top slot" also supported various other hardware additions, such as telephone dialers, a speech synthesiser, barcode reader and even a dedicated thermal printer. This latter was used by several banks as a counter-top exchange rate calculator for some years. As it was easy to get hardware specifications, numerous bespoke devices were developed by small companies such as A/D converters and even an interface to the entire range of Mitutoya measuring equipment, allowing it to be used in quality control for various car manufacturers. Later models in the Organiser II range offered other hardware improvements, with 4-line displays, and also models were introduced with 32, 64 and 96KB RAM.
 Subsequent hand-held devices
The name "Organiser" was not used for later Psion handhelds, such as the "SIBO" family Psion Series 3 and the 32-bit Psion Series 5 machines which were of a clamshell design with a QWERTY keyboard. In terms of hardware architecture and operating system, these had no links to the earlier "Organiser" range, other than the end user programming language which shared a great deal of structure with OPL.
The "SIBO" family name stood for "SIxteen Bit Organiser" and the improved version of the OPL language (with window and focus controls) was at the root of what was later sold as the Symbian operating system, which until 2010 was the most widely used OS in smartphones, being in 2011 displaced by Google's Android OS. This change was more significant than appeared at the time. The consumer level 'high' programming language still shares features with OPL, but the developer toolkits were from then on focused on programmers familiar with C and only the Symbian operating system remains.
The first similar device made in the USA didn't appear until 1985 and was manufactured by Validec.
- The Psion Organiser II Homepage - Everything you ever wanted to know about the Psion Organiser II, and more...
- Psion website - the operational division of Psion PLC.
- Psion Organiser History - website by Steve Litchfield.
- A detailed history of Psion around the time of the Series 5
- "Wall of Fame - Blackberry vs Psion" (swf). The Gadget Show. United Kingdom: Channel 5 Broadcasting Ltd. 2009-04-30. Retrieved 2009-04-01. "Each week on the Wall of Fame, we look at one particular area of gadgetry and choose the most iconic gadget from that category to join our Wall of Fame. ... And this week we're putting the Psion Organiser up against the ubiquitous BlackBerry."
- 'Canadian & UK Psion Advertisements 1984'
- "Gartner Says Sales of Mobile Devices in Second Quarter of 2011 Grew 16.5 Percent Year-on-Year; Smartphone Sales Grew 74 Percent". Gartner. 2011-08-11.
- "Waiters Trade Pad for Computer : 'Hold the Mayo' Note Goes to the Chef on a Printout". Los Angeles Times. 1985-03-10.