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Program Java devices -- An overview

Get up to speed on Java for small devices

By Bill Day, JavaWorld.com, 07/24/99

Today, we can see three distinct but overlapping eras of computing:

• Mainframe era: one computer, many people
• PC era: one person, one computer
• Ubiquitous-computing era: one person, many computers

Most of us use more computers embedded in devices and appliances than we do PCs, workstations, and mainframes combined. For instance, a quick inventory of my average workday shows that I use a laptop, a couple of servers, and a workstation. But the car I use to commute to work each day has many more CPUs than all of those traditional computers put together! When we include the computer chips in mobile phones, Palm handhelds, microwave ovens, Ethernet hubs and the communication equipment we use at work (the phone system, and so on), you can see that we're already firmly planted in the era of ubiquitous computing.

Not only are CPUs everywhere, but almost all of our interactions with CPUs involve (or very soon will involve) interactions with networks. How can you as a programmer take advantage of computers and networks embedded everywhere in heterogeneous devices and environments?

Java technology enables ubiquitous network computing

Many articles on the history of Java describe its early days as having been device-oriented. Java was originally designed for nontraditional computing devices; over time, it moved up into desktops and servers. From the beginning, Java's small bytecode size, ability to move objects around networks, and cross-platform portability were engineered to enable programming for small, mobile, heterogeneous devices. It luckily turned out that these features were also quite useful in an interconnected, Net-based world on bigger computers.

Java technology has come full circle, and programming devices with Java is once again on the rise. In this column, I will examine the various APIs, tools, and products available for Java programming for various consumer devices, such as personal digital assistants (PDAs), mobile phones, pagers, and similar embedded computers.

As these articles unfold, I hope you will gain a greater appreciation of both what Java can do for these devices and how you can take advantage of them in future projects.

Major Java device APIs and initiatives

Sun and its partners are building a number of Java device environments and APIs:

• PersonalJava, including numerous implementations from RTOS (Realtime Operating System) vendors. It supports consumer devices with a GUI and network connection.
• EmbeddedJava, for devices with intermittent or no network connection and often no GUI. It is highly configurable to include only those classes and VM features needed for a particular device.
• JavaCard, including Dallas Semiconductor's iButton implementation (the ever popular Java ring being one form factor for its delivery).
• Java 2 Platform, Micro Edition (J2ME) and the K Virtual Machine (KVM) for consumer devices are the latest additions. Early preview versions were demonstrated at JavaOne (June 1999) running on Motorola PageWriter2000x, Palm III and V hand-held devices, Bull point-of-sale (POS) terminals, and next generation mobile phones from Matsushita/Panasonic and other manufacturers targeting NTT DoCoMo's i-mode service. They will enable Jini support for small devices, as well as enable splitting up computing functionality between device and server, so that device footprint can be minimized.
• Symbian, a partnership between Nokia, Ericsson, Motorola, and Matsushita/Panasonic, providing Java support for the EPOC32 mobile phone and wireless communicator operating system.

In addition, several other companies have independent clean-room Java for consumer and embedded device initiatives. Among these, the most talked about technologies include: