On a typical desktop PC, data and programs are stored on a disk drive. The use of a flash memory card is analogous to a disk drive on a desktop system.
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Flash memory cards are available in a number of different types and sizes, 14 Jon Trinder ranging in size from 16MB approx. SD cards incorporate encryption functions and are faster than MMC as they have a 4-bit interface compared to the single bit MMC interface. MiniSD is less than half the size of a normal SD card. Special adapters are available to allow them to be used in normal SD card slots. Limited to a maximum size of MB.
CompactFlash is still popular for use in high-end digital cameras. This is the same as running a program on a desktop system; the program is first loaded from the storage device normally your hard drive into RAM, where it is then executed. Memory cards are used by many devices so can provide a simple means of transferring data between other devices, for example images could be transferred from a digital camera and then viewed or e-mailed using the PDA.
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Communications PDAs now use various methods for exchanging information. Selection of the device to communicate with is by simply pointing at it. Bluetooth: A short distance radio system with a range of around ten metres. Bluetooth and infrared are complementary technologies, each with its own advantages in different situations.
Infrared has some advantages over other radio Mobile technologies and systems 15 based wireless technologies, as it is less likely to be intercepted by other users and is line of sight. For beaming a business card, it is easy to select who you are beaming the card to by pointing at their machine. With Bluetooth, however, the selection is much more time consuming as the sending device has to first locate and pair with the intended receiving device.
This may not take long if there are only a few other Bluetooth devices in the vicinity, but if there are many such as at a conference or classroom it can.
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The two main variations are known as Recharging a PDA usually takes 2—4 hours. Lithium Ion and Lithium Polymer batteries do not need to be fully discharged prior to charging and will benefit from frequent top-up charging Buchmann Manufacturers claim a fully charged battery in a PDA is sufficient for 5—15 days of normal use.
During sleep mode, power is still supplied to the memory so that data and programs in the memory are not lost. It is important that batteries are not allowed to run out as any data stored in the PDA memory, e. Some systems include auxiliary internal batteries specifically to maintain the memory in the event that the main batteries fail, but this may not last long.
Most systems will give a warning when the battery level is getting low and refuse to power on before the batteries are totally exhausted, thus conserving the data in memory for a short while. When they run low, replacements can be easily obtained. PDA designers have employed various strategies to maximize battery life.
For instance, whilst using a calendar application that is displaying static information the processor 16 Jon Trinder and many peripherals can be turned off. Current systems now employ more intelligent and adaptive mechanisms to reduce power consumption. By varying the supply voltage of the CPU and optimizing the speed the processor is running at, considerable power saving may be made with a consequent increase in battery life.
There are also a number of devices that use a version of Linux. The operating system is responsible for managing the resources of any computer. An API is a set of functions that is used by application programs.
The API provides basic building blocks that a programmer combines with other functions to create a program. The programmer interacts with hardware through the API — this is important as it allows some parts of the underlying hardware to change without the need for new versions of a program.
Mobile technologies and systems 17 Synching between one desktop or laptop and one handheld is straightforward. It is also easy to synch one handheld to two or more desktops or laptops. Synching a group of handhelds, such as with a class of students, to a single desktop or laptop, is problematic — for example, where some data is public and some is personal, the computers must be specifically instructed to avoid accidentally deleting or distributing the personal data.
It is a technical issue Hansmann et al. Software and content Although the PDA was originally intended to act as an electronic replacement for personal organizers, developers have produced a rich variety of other innovative solutions. A big shock for the new PDA user is that when looking for a particular type of application, they are faced with having to choose one from a large number on offer! There are a large number of high-quality free applications available and many are supplied with source code enabling them to be modified by a user with programming knowledge.
There is plenty of choice in the field of PDA software and for almost every type of application there are a number of competing products. Many companies produce different versions of an application to suit each of the most popular PDA platforms and may also have a version that will operate on a PC. An application program is written for a specific operating system running on a specific set of hardware.
A separate version of each must be used depending on the device there is some interoperability with applications written for mobile versions of JAVA. An evaluation version is normally available for no cost and can be used on a trial basis for a specified period typically 7—30 days. If you wish to continue to use the software after the trial period, you are required to buy and register the software. There are a number of download sites where shareware software can be downloaded and registered. Once an application is registered, the author sends a registration key to unlock the software and remove any nag screens or limitations.
Google, the search engine, has a PalmOS-specific version www. It is easy to produce your own e-book and programs to convert existing documents into the various e-book formats are available for a modest cost. Some types of e-books enable content to be copy protected. News Readers: daily news channels can be downloaded for off-line reading via popular applications such as AvantGo and Mobipocket. There are on-line resources providing databases of specialized reference information for the most popular handheld database formats.
Many of these are free. Software development If one of the many PDA applications does not quite provide the functionality that you require then you may want to write your own. PDA users from many professions have written their own software to provide specialized applications. Writing a customized application does not have to be daunting depending on the type of application you require — for data collection many database applications can be customized to provide the required data entry forms.
There are limitations that must be taken into consideration when designing an application for use on a PDA. Apart from the limitations enforced by the size of the display, many devices do not have a keyboard, and rely on handwriting recognition. Even on machines with a miniature keyboard entering large amounts of text is time-consuming. It is better to provide choices for a user to select from, using interface devices such as lists and check boxes Palm J AVA Ideally, it should be possible to develop a platform-independent application that could be used on any of the currently available systems and easily adaptable to future devices.
Rather than a program being written to run on a specific platform it is instead written for a virtual machine. Thus a program written for the virtual machine may run on any platform for which there is a virtual machine interpreter program available.
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This concept is the basis for the JAVA programming language. Programs written in JAVA are compiled into virtual machine instructions. There are implementations of JAVA Virtual Machines for many types of system, from small, embedded devices to large mainframe systems. Obviously the capabilities in speed and storage vary widely between that of a small, embedded processor used in a consumer device such as a phone and the capabilities of a multiprocessor workstation or server.
To support these variations of system capabilities there are a number of subsets of the full JAVA implementation. T h e e v o l u t i o n o f P DA s Design approaches There are now wide varieties of PDA type devices and to understand the differences between apparently similar devices we need to look at how PDAs have evolved. A major factor in this evolution is the operating system. Palm and Microsoft, for example, approached the design of the PDA and its operating system in different ways.
The Microsoft strategy was to produce a cut-down version of its Windows desktop operating system. Microsoft produced the operating system with other companies such as Hewlett Packard 20 Jon Trinder designing the hardware. The first devices running Windows CE, as it is known, were of clamshell design. As Palm designed both the hardware and software, they were able to make quick tradeoffs between the two.
Palm designed a new operating system and user interface specifically for use on a small-screen device that was powered by batteries. Instead, they designed the system to be easy to learn and quick to use. A lot of thought went into the user interface and the built in PIM applications to reduce the number of steps required to perform a task.
The effect on the hardware requirements of the different approaches to design made by Palm and Microsoft can be seen in Table 2. Convergence As technology continues to improve it will be possible to integrate even more features into small handheld devices and we are likely to see many different types of hybrid device appearing.
Different functions may be combined for convenience or to complement existing features. A danger of combining functionality in one device is that compromises have to be made with the interface and this might reduce the overall usability of the device. However, there are many applications for which a combined device may not be suitable or desirable.
Combinations that appeal to the public may not be suitable for use in business and education environments. For example, many phones now incorporate a camera but some companies and schools ban cameras on their premises and this includes those built into devices such as phones and PDAs. As we have said above, technologies such as cameras and MP3 players are being integrated into many different types of handheld and mobile device, such as Table 2. It seems likely we may all own a variety of devices, many of which overlap in their purpose.