SIon> (jar) A compressed archive file containing Javaclass files, filename extenSIon: ".jar". The Java Development Kit contains a tool called "jar" for creating .jar files, SImilar to the standard Unixtar command. As well as archiving and compresSIng the Java class files, it also inserts a "manifest" file which can contain information about the class files, such as a {digital SIgnature}. Combining class files into a SIngle archive file makes it posSIble to download them in a SIngle HTTP transaction. This, and the compresSIon, speeds up execution of Java programs delivered via the Internet. (2001}-02-03)