Java Programing laungage

The configuration Layer is define the basic defines the basic run-time environment as a set of core classes and a specific JVM that run on specific kind of device based on memory constraints and processor power. These are of two type - Connection Device Configuration (CDC) use for large memory device, memory more than 2 MB and Connection Limited Device Configuration (CLDC) use for small memory device, memory small than 512 KB.

1.Connected Device Configuration (CDC)

CDC is a framework for Java ME defines the basic set of APIs, library, and virtual-machine features for resource-constrained devices like pager, mobile phones, and mainstream Personal Digital Assistants (PDAs) and must be implemented into applications. It provide a standard platform for developers for developing some complex application for embedded systems( from pager to set-top boxes) by combined with one or more than one Profiles. CDC was developed under the Java Community Process. It specifies a full Java virtual Machine (JVM) called CVM (C Virtual Machine) and is used for 32- bit architectures requiring more than 2 MB of memory.

CDC Memory:CDC target devices run a 32-bit microprocessor and have more than 2 MB of memory, which is needed to store the C virtual machine and libraries.

Specification of CDC launch under the Java Community Process

CDC 1.0.2 (Java Specification Request (JSR) 36 ).
CDC 1.1.2 (Java Specification Request (JSR) 218 ).

CDC requirements

Full Java language support include exception handling and floating pointer support.
Full Internationalization support.
Full Java Virtual Machine (JVM) support in form of C Virtual Machine (CVM) with large amount of memory about 2 MB.

Core application programming interfaces (APIs) of CDC

CDC support number of optional packages like Java Remote Method Invocation (RMI) and Java DataBase Connectivity (JDBC), that allow developers to access extra functionality within the restricted resource constraints of a Java ME device.

java.rmi
java.sql and javax.sql

2. Connected Limited Device Configuration (CLDC)

CLDC is a framework for ME defines the the basic set of APIs, library, and virtual-machine features for resource-constrained devices like pager, mobile phones, and mainstream Personal Digital Assistants (PDAs) and must be implemented into applications.

It provide a standard platform for developers for developing some complex applications on embedded devices with limited resource such as phones and pager by combined with one or more than one Profiles. CLDC was developed under the Java Community Process. CLDC is build on “scale down” version of Java virtual Machine (JVM) called KVM (Kilobytes Virtual Machine) for 16 - bit or 32- bit device with limited amounts of memory like 512 KB.

CLDC memory - CLDC target devices with slow network connections, limited power (often battery operated), 128 KB or more of non-volatile memory, and 32 KB or more of volatile memory. Volatile memory is non-persistent and has no write protection, meaning if the device is turned off, the contents of volatile memory are lost.

With non-volatile memory, contents are persistent and write protected. CLDC devices use non-volatile memory to store the run-time libraries and KVM, or another virtual machine created for a particular device. Volatile memory is used for allocating run-time memory.

Specification of CLDC launch under the Java Community Process

CLCD 1.0 (Java Specification Request (JSR) 30).
CLCD 1.1 (Java Specification Request (JSR) 139).

CLDC requirements

Full Java language support except error handling, floating pointer support, and finalization.
Limited internationalization support.
Full Java Virtual Machine (JVM) support in form of Kilobytes Virtual Machine (KVM) with limited amount of memory.
Inherited classes - all classes not specific to CLDC must be subsets of J2SE 1.3 classes.
Classes specific to CLDC are in javax.microedition package and subpackages.