Abstract: A system for accessing resources, such as bitmaps, fonts and sound files is provided. Typically, resources of this type are accessed as files from Java code. The data is read into dynamic (RAM) memory as a byte array in a Java object, and at least one other copy of the byte array is made in order to process the resource data, such as rendering an image to a display. The invention provides a mechanism for accessing the resource data directly from ROM, without making intermediate copies in RAM. Each resource can have a unique key or string in a logical table. Values associated with the keys are pointers to the data stored in ROM. The pointers are passed directly to the methods for processing the data on the hardware, bypassing the need to have the data become a temporary Java object. The saving in memory use is particularly advantageous for constrained memory devices.

Abstract: A method, system, and computer program product for transparently loading resources (such as stored bitmaps, images, fonts, and sound files) from read-only memory (“ROM”) for an application program executing on a Java Virtual Machine (“JVM”). Typically, the invention will be used on an embedded computing device which has no disk storage and no file system software. A novel class loader is described, which loads resources from ROM and returns an input stream object as is expected by the existing application program. Therefore, when using the present invention, no change is required to existing application code to use resources stored in ROM. (In addition, no change to existing applications is required in order to invoke the code of the present invention.) The invention may be used with programs written in the Java programming language, or with programs written in other languages that execute on a JVM.

Abstract: In typical Java and other interpreted programming language environments, the code is stored in ROM in a semi-processed state, .class files containing byte codes. When the device is turned on, a virtual machine resolves references and links the .class file in RAM to permit desired applications to be run. In the invention, the .class files are further pre-processed to select the data which will not change or require updating. This data is packaged into memory image files containing internal data pre-linking this data. The memory image files are stored in ROM and are accessible from ROM by the virtual machine at runtime. Only elements that will be updated, such as the objects themselves, must be instantiated in RAM at runtime. This reduces the amount of RAM needed to run the application. In an environment with memory constraints, the reduction in RAM requirements permits more RAM to be made available for application use.