A typical PDA has a touchscreen for navigation, a memory card slot for data storage, and
IrDA,
Bluetooth and/or
Wi-Fi. However, some PDAs may not have a touchscreen, using
soft keys, a directional pad, and a numeric keypad or a
thumb keyboard for input. To have the functions expected of a PDA, a device's software typically includes an
appointment calendar, Touchscreen PDAs intended for business use, such as the
BlackBerry and
Palm Treo, usually also offered full keyboards and
scroll wheels or thumbwheels to facilitate data entry and navigation. Multiple touchscreen PDAs supported some form of external keyboard as well. Specialized folding keyboards, which offer a full-sized keyboard but collapse into a compact size for transport, were made available for multiple models. External keyboards may have attached to the PDA directly, using a cable, or using wireless technology such as infrared or Bluetooth to connect to the PDA. Newer PDAs, such as the
HTC HD2,
Palm Pre,
Pre Plus,
Pixi, and
Pixi Plus, as well as devices running the
Android operating system, included more advanced forms of touchscreen that could register multiple touches simultaneously. These "
multi-touch" displays allowed for more sophisticated interfaces using various gestures entered with one or more fingers.
Memory cards Although many early PDAs did not have
memory card slots, later models had either some form of
Secure Digital (SD) slot, or directly by using an expansion card that provided an
Ethernet port.
Wireless connectivity Many later PDAs use Bluetooth, a popular wireless protocol for mobile devices. Bluetooth can be used to connect keyboards, headsets,
GPS receivers, and other nearby accessories. It is also possible to transfer files between PDAs that have Bluetooth. Multiple PDAs have Wi-Fi wireless network connectivity and can connect to Wi-Fi hotspots. All smartphones, and some other PDAs, can connect to
wireless wide area networks, such as those provided by cellular telecommunications companies. Older PDAs, from the 1990s to 2006, typically had an
IrDA (
infrared) port allowing short-range, line-of-sight wireless communication. Few later models used this technology, as it had been supplanted by Bluetooth and Wi-Fi. IrDA allows communication between two PDAs, or between a PDA and any device with an IrDA port or adapter. Some contemporary printers have IrDA receivers, allowing IrDA-equipped PDAs to print to them, if the PDA's
operating system supports it. Universal PDA keyboards designed for these older PDAs use infrared technology, due to cost and a lack of wireless interference.
Synchronization Most PDAs were able to
synchronize their data with applications on a user's computer, allowing the user to update contact, schedule, or other information on their computer, using software such as
Microsoft Outlook or
ACT!. They could have that same data transferred to the PDA—or transfer updated information from the PDA back to the computer, eliminating the need for the user to update their data in two places. Synchronization also prevented the loss of information stored on the device if it was lost, stolen, or destroyed. When a PDA was repaired or replaced, it could likewise be "re-synced" with the computer, restoring the user's data. Some users found that data input was quicker on their computer than on their PDA since text input via a touchscreen or small-scale keyboard was slower than a full-size keyboard. Transferring data to a PDA via the computer was, therefore, a lot quicker than having to manually input all data on the handheld device. Data synchronization was done through
synchronization software provided with the handheld, or sometimes with the computer's operating system. Examples of synchronization software include: •
HotSync Manager, for
Palm OS PDAs • Microsoft
ActiveSync, used by
Windows XP and older Windows operating systems to synchronize with
Windows Mobile,
Pocket PC, and
Windows CE PDAs, as well as PDAs running
iOS, Palm OS, and
Symbian • Microsoft
Windows Mobile Device Center for
Windows Vista, which supports Windows Mobile and
Pocket PC devices • Apple
iTunes used on
Mac OS X and Microsoft Windows to sync iOS devices •
iSync, included with Mac OS X, can synchronize many
SyncML-enabled PDAs • BlackBerry Desktop Software, used to sync
BlackBerry devices. These programs allowed the PDA to be synchronized with a
personal information manager, which may be part of the computer's operating system, provided with the PDA, or sold separately by a third party. For example, the RIM BlackBerry came with RIM's
Desktop Manager program, which can synchronize to both Microsoft Outlook and ACT!. Other PDAs came only with their own proprietary software. For example, some early Palm OS PDAs came only with
Palm Desktop, while later Palm PDAs—such as the
Treo 650—have the ability to sync to Palm Desktop or Microsoft Outlook. Microsoft's ActiveSync and Windows Mobile Device Center only synchronized with Microsoft Outlook or
Microsoft Exchange Server. Third-party synchronization software was also available for some PDAs from companies like CommonTime and
CompanionLink. Third-party software can be used to synchronize PDAs to other personal information managers that are not supported by the PDA manufacturers (for example, GoldMine and
IBM Lotus Notes).
Wireless synchronization Some PDAs could synchronize some or all of their data using their wireless networking capabilities, rather than having to be directly connected to a personal computer via a cable (or dock/cradle). Devices running Palm's
webOS or Google's
Android operating system would primarily sync with the
cloud. For example, if
Gmail was used, information in contacts, email, and calendars can be synchronized between the PDA and Google's servers. RIM sold
BlackBerry Enterprise Server to corporations so that corporate BlackBerry users could wirelessly synchronize their PDAs with the company's
Microsoft Exchange Server, IBM
Lotus Domino, or
Novell GroupWise servers. Email, calendar entries, contacts, tasks, and memos kept on the company's server were automatically synchronized with the BlackBerry. ==Operating systems of PDAs==