# Introduction

The following sections of this document shall prove useful as a reference when developing applications for MicroEJ. They cover concepts essential to MicroEJ Applications design.

In addition to these sections, by going to https://developer.microej.com/, you can access a number of helpful resources such as:

MicroEJ Applications are developed as standard Java applications on Eclipse JDT, using Foundation Libraries. MicroEJ SDK allows you to run / debug / deploy MicroEJ Applications on a MicroEJ Platform.

Two kinds of applications can be developed on MicroEJ: MicroEJ Standalone Applications and MicroEJ Sanboxed Applications.

A MicroEJ Standalone Application is a MicroEJ Application that is directly linked to the C code to produce a MicroEJ Firmware. Such application must define a main entry point, i.e. a class containing a public static void main(String[]) method. MicroEJ Standalone Applications are developed using MicroEJ SDK.

A MicroEJ Sandboxed Application is a MicroEJ Application that can run over a Multi-Sandbox Firmware. It can be linked either statically or dynamically. If it is statically linked, it is then called a System Application as it is part of the initial image and cannot be removed. MicroEJ Sandboxed Applications are developed using MicroEJ Studio.