Introduction - Beginning J2ME: From Novice to Professional - page 5

You can find more information at the CLDC home page, http://java.sun.com/products/
cldc/ . Most deployed devices implement CLDC 1.0, but CLDC 1.1 devices are making their way
onto the market as this is written. CLDC 1.1 includes enhancements to CLDC 1.0, including
support for floating-point data types.

Profiles
A profile is layered on top of a configuration, adding the APIs and specifications necessary to
develop applications for a specific family of devices.

Current Profiles
Several different profiles are being developed under the Java Community Process. Table 1-1
(shown earlier) provides a bird's-eye view.
The Foundation Profile is a specification for devices that can support a rich networked
J2ME environment. It does not support a user interface; other profiles can be layered on top of
the Foundation Profile to add user interface support and other functionality.
Layered on top of the Foundation Profile are the Personal Basis Profile and the Personal
Profile. The combination of CDC + Foundation Profile + Personal Basis Profile + Personal Profile
is designed as the next generation of the PersonalJava application runtime environment (see
http://java.sun.com/products/personaljava/ ). As such, the Personal Profile has the specific
goal of backward compatibility with previous versions of PersonalJava.
The PDA Profile (PDAP), which is built on CLDC, is designed for palmtop devices with a
minimum of 512KB combined ROM and RAM (and a maximum of 16MB). It sits midway
between the Mobile Information Device Profile (MIDP) and the Personal Profile. It includes an
application model based on MIDlets but uses a subset of the J2SE Abstract Windowing Toolkit
(AWT) for graphic user interface. Although the PDAP specification is nearly finished, to our
knowledge no hardware manufacturer has announced that it will be implementing PDAP. The
J2ME world currently is covered by MIDP on the small end and Personal Profile on the higher end.

Mobile Information Device Profile
The focus of this topic is the Mobile Information Device Profile (MIDP). According to the MIDP 2.0
specification (JSR-118), a Mobile Information Device has the following characteristics:

• A minimum of 256KB of ROM for the MIDP implementation (this is in addition to the

requirements of the CLDC)

• A minimum of 128KB of RAM for the Java runtime heap

• A minimum of 8KB of nonvolatile writable memory for persistent data

• A screen of at least 96×54 pixels

• Some capacity for input, either by keypad, keyboard, or touch screen

• Two-way network connection, possibly intermittent