Editing Memory protection (section)

=== Capability-based addressing ===
{{Main|Capability-based addressing}}
[[Capability-based addressing]] is a method of memory protection that is unused in modern commercial computers. In this method, [[pointer (computer programming)|pointers]] are replaced by protected objects (called ''capabilities'') that can only be created using [[Privilege (computing)|privileged]] instructions which may only be executed by the kernel, or some other process authorized to do so.{{citation needed|date=August 2012}} This effectively lets the kernel control which processes may access which objects in memory, with no need to use separate address spaces or [[context switch]]es. Only a few commercial products used capability based security: [[Plessey System 250]], [[IBM System/38]], [[Intel iAPX 432]] [[Instruction set|architecture]] and [[KeyKOS]]. Capability approaches are widely used in research systems such as [[EROS (microkernel)|EROS]] and Combex DARPA browser. They are used conceptually as the basis for some [[virtual machine]]s, most notably [[Smalltalk]] and [[Java (software platform)|Java]]. Currently, the DARPA-funded [[Capability_Hardware_Enhanced_RISC_Instructions|CHERI]] project at University of Cambridge is working to create a modern capability machine that also supports legacy software.