Pocket PC Devices

What began as the Windows CE operating system quickly changed into the Microsoft Pocket PC OS after CE's unpopularity became glaringly apparent. Microsoft dropped the Windows CE label after version 3.0 and began marketing its device and operating system as the Pocket PC only. (Although some devices are called Pocket PCs, for the purposes of this section, the term Pocket PC will be used to designate the OS itself.) The Pocket PC can surf the actual Web and can stream Windows audio and video. Surprisingly, Palm has a bigger market share, even though it does not provide full Web browsing capability. Microsoft targets the business market, whereas Palm markets itself as a personal organizer. Where Palm boasts name brand recognition, these devices boast functionality. The battery life, however, on a Windows CE device is far shorter than that of a Palm OS device. The battery life is measured in hours and maybe days, versus Palm's weeks.

Compaq's iPaq PDA runs on the Microsoft Pocket PC OS and uses the Intel SA-1110 206MHz processor, much faster than the Handspring Edge processor. It has 16MB flash memory and 32MB SDRAM. It integrates seamlessly with PC cards and CompactFlash and can run slimmed-down versions of Microsoft's Office products, Pocket Excel or Pocket Word. One nice feature of this OS is that it supports a variety of processors, unlike the Palm OS. Processor-specific information is contained in a few spaces in the Pocket PC OS but is assignable after a processor is chosen for a given device that will use this Microsoft Pocket PC OS.

Pocket PC supports both 1K and 4K page sizes so that it can be used on processors that support either size. Applications developed for use in a Pocket PC OS must be compiled in a processor-specific compiler. If an application is designed for use with more than one processor, it must be compiled on each compiler specific to a certain processor or family of processors. The OS supports 32 concurrent processes. Communication among processes is facilitated through Windows messaging, similar to how it works in other Windows OSs.

A Pocket PC system supports RAM, ROM, and flash memory. RAM is used to provide buffers for application data and to run applications. The OS provides battery-backed RAM, which gives the devices their instant on feature. ROM is used to hold programs. It has persistent contents and can be likened to a file system or disk storage space in a traditional PC. ROM contains the files that make up the OS. To prevent inadvertent overwrites of the OS-critical files, physically inserting a new ROM chip is necessary to upgrade the operating system. The alternative memory option is flash memory. It can be upgraded, but the OS's entire image must be set in, byte by byte.

The GWES (Graphics, Windowing, and Events Subsystem) provides services for the device. It includes power management, window and dialog management, user input services, and the graphics interface. The Graphical Device Interface (GDI) helps render text and graphics. GDI processes can be set in place to create windows and dialogs and interact with the user. Standard functions for each of these are available. The input support in GWES allows the use of various input mechanisms, a keyboard, a touch pad, or even a thumbwheel-type option.

The option to induce power management is an optional module. Most devices that feature the Pocket PC OS require power management, however, because they run applications that are very taxing on the battery. The power management of an extension module may be distinct from that of the device itself. There are four possible states of power:

1. No power. Only before the first configuration.

2. On. Full power.

3. Idle. On but inactive.

4. Suspend. When turned off, minimal power, but retains settings and programs. Power is suspended to peripherals and the CPU.

5. Critical off. Low battery causes cutting off power to the CPU and peripherals until recharged.

The Pocket PC file system allows access to data stored in all three types of memory, as well as extension devices as files or folders. The file system is based on file allocation tables (FAT). It works with extension storage cards that can be partitioned into sections named volumes. The volumes are accessible from the CE root directory. The Registry is part of this OS's file system as well. It is used by the OS and its modules, device drivers, and applications. Configuration information is typically stored in the registry and accessed upon initiation of an application. That same configuration information is also stored back to the registry upon termination of the application.

Network connectivity is possible in various ways with these devices, as with Palm OS devices. IrDA connectivity is integrated into devices, and serial or USB connections are possible with a cable or by docking in a cradle. PC cards and CompactFlash enable Pocket PCs to connect via 56Kbps modems or Ethernet, not via a cradle, as in Palm OSs. Whereas Palms cannot connect to wireless LANs, Pocket PCs can, with the use of a PC card expansion. Also, using a PC card, CompactFlash, or an IrDA link to a cell phone, Pocket PCs can connect to cellular networks.