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The term "P-code machine" is applied generically to all such machines (such as the Java virtual machine (JVM) and MATLAB pre-compiled code), as well as specific implementations using those machines. One of the most notable uses of P-Code machines is the P-Machine of the Pascal-P system.
UCSD p-System achieved machine independence by defining a virtual machine, called the p-Machine (or pseudo-machine, which many users began to call the "Pascal-machine" like the OS—although UCSD documentation always used "pseudo-machine") with its own instruction set called p-code (or pseudo-code).
Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter.Unlike human-readable [1] source code, bytecodes are compact numeric codes, constants, and references (normally numeric addresses) that encode the result of compiler parsing and performing semantic analysis of things like type, scope, and nesting depths of ...
A notable 1966 example was the O-code machine, a virtual machine that executes O-code (object code) emitted by the front end of the BCPL compiler. This abstraction allowed the compiler to be easily ported to a new architecture by implementing a new back end that took the existing O-code and compiled it to machine code for the underlying ...
P-code is an alternative term for bytecode, machine-independent code that achieves independence by targeting a p-code machine, a virtual machine designed for running p-code rather than the intention to emulate any specific hardware architecture. P-code may also refer to:
the UCSD Pascal p-machine; which closely resembled Burroughs; the Niklaus Wirth p-code machine; Smalltalk; the Java virtual machine instruction set (note that only the abstract instruction set is stack based, HotSpot, the Sun Java Virtual Machine for instance, does not implement the actual interpreter in software, but as handwritten assembly stubs)
This idea originated no later than the 1960s, with the IBM M44/44X, and in the late 1970s the UCSD Pascal system was developed to produce and interpret p-code. UCSD Pascal (along with the Smalltalk virtual machine) was a key influence on the design of the JVM, as is cited by James Gosling. [citation needed]
Any language targeting a virtual machine or p-code machine can be considered an intermediate language: Java bytecode; Microsoft's Common Intermediate Language is an intermediate language designed to be shared by all compilers for the .NET Framework, before static or dynamic compilation to machine code.