The Zire Series was Palm, Inc's "consumer-grade" brand of Personal Digital Assistant.
The lower-end models emphasized price — Palm's original Zire model was the first PDA under $100 from a major manufacturer — and the higher-end models emphasized multimedia capacity, including features like cameras and audio playback functions suitable for listening to MP3s.
The Palm Zire and Palm Zire 21 were inexpensive and are differentiated from the rest of Palm's line by having monochrome screens without backlighting, having only two quickbuttons instead of four, and a traditional up/down navigation button instead of a 5-Way Navigator, though both of these entry-level models are lightweight (3.8oz or 108g), sporting a white front with a matte gray plastic back.
The Zire, released in the fourth quarter of 2002 (also known as the m150), is the handheld responsible for starting the value-conscious handheld craze. It sported only 2 MB RAM, a 16MHz Motorola DragonBall EZ processor, and Palm OS 4.1.x. The Zire was superseded by the Zire 21 at the release of the "First Breed of PIM Plus Handhelds" on fourth quarter 2003.
The Zire 21, released at the same time as the Tungsten T3 and Tungsten E, sported an improved PIM suite (known as the Palm PIM Plus), a 126MHz TI OMAP311 ARM-Compliant Processor, 8 MB RAM, and Palm OS 5.2.1.
Neither the Zire nor the Zire 21 had SD/SDIO/MMC expansion, which caused the devices to be vehemently shunned by venerable handheld aficionados. As of August 2005, both of these handhelds had been discontinued, making the Palm Zire 31 the entry-level Palm-branded PDA citing a strong demand for color.
The Zire 21 was capable of displaying PDF files using the free Adobe Reader for Palm OS version 3. Like most palm handhelds, text from the PDF file could be copied and pasted into other applications such as Memo Pad, greatly enhancing the utility of this cheap device. It was capable of, in effect, acting as a portable word processor, albeit a very basic one.