Squawk virtual machine

Squawk
Developer(s)	Sun Microsystems
Initial release	April 2002; 22 years ago
Repository	github.com/tomatsu/squawk
Written in	C and Java
Operating system	Cross-platform
Type	Java virtual machine
License	GNU General Public License
Website	java.net/projects/squawk/pages/SquawkDevelopment

Squawk is a Java micro edition virtual machine for embedded system and small devices. Most virtual machines for the Java platform are written in low level native languages such as C/C++ and assembler; what makes Squawk different is that Squawk's core is mostly written in Java (this is called a meta-circular interpreter). A Java implementation provides ease of portability, and integration of virtual machine and application resources such as objects, threads, and operating-system interfaces.

The Squawk Virtual Machine figure can be simplified as:

Write as much of the VM in Java as possible
Targeting small, resource constrained devices
Enable Java for micro-embedded development

The research project was inspired by Squeak. Squawk has a Java ME heritage and features a small memory footprint.^[1] It was developed to be simple with minimal external dependencies. Its simplicity made it portable and easy to debug and maintain. Squawk also provides an isolated mechanism by which an application is represented as an object. In Squawk, one or more applications can run in the single JVM. Conceptually, each application is completely isolated from all other applications.