P-code


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P-code

(language)
The intermediate language produced by the Pascal-P compiler. P-code is the assembly language for a hypothetical stack machine, the P-machine, said to imitate the instruction set of the Burroughs 6700.

The term was first used in the Wirth reference below. Byte articles on writing a Pascal Compiler in Northstar BASIC (ca Aug 1978) also used the term.

P-code was initially the intermediate code generated by the P2 compiler from ETH Zurich. P-code was later used as the intermediate language in the UCSD Pascal System, and in its two main derivatives, Apple Pascal and the UCSD P-system.

Variants: P2 P-code, P4 P-code, UCSD P-code, LASL P-code.

[Algorithms + Data Structures = Programs, N. Wirth, P-H 1976].

["A Comparison of PASCAL Intermediate Languages", P.A. Nelson, SIGPLAN Notices 14(8):208-213, Aug 1979].

intermediate language

A language that is generated from programming source code, but that cannot be directly executed by the CPU. Also called "bytecode," "p-code," "pseudocode" or "pseudo language," the intermediate language (IL) is platform independent. It can be run in any computer environment that has a runtime engine for the language.

In order to execute the intermediate language program, it must be interpreted a line at a time into machine language when it is run or compiled entirely into machine language just before it is run or compiled entirely ahead of time and run when required.

A Popular Architecture
Visual Basic and Java are notable examples of programming languages that generate an intermediate language. Microsoft's .NET and Common Language Infrastructure (CLI), the ECMA standard version of .NET, also generate an intermediate language (see CLR and CLI). See Java Virtual Machine, bytecode, managed code and runtime environment.
References in periodicals archive ?
First, the HC signal is correlated with locally generated reference signal under the help of instantaneous nominal satellite and HC receiver position to find out the delay information of primary code (P-code in our case) in every pulse repetition interval (PRI).
[L.sub.1] signal consists of C/A code and P-Code with minimum received power of -160 dBW and -163 dBW respectively.
P-Code is known as the Precise Positioning Service (PPS), where the U.S.
Comparison tests between live jamming and the RJU injected jamming have been made for military (p-code) receivers.
Military devices tuned to the GPS P-Code frequency can calculate position to within a few meters.
Since the precision of range measurement is determined, in part, by chip wavelength, shorter wavelengths will yield higher precision and the 30 m wavelength of the P-code recognizes that consideration.
L2 is modulated only by the encrypted P-code signal.
The DOD controls C/A and P-code with different accuracy and availability of the GPS signal, and recent Presidential mandates provide for the selective-availability aspects of the GPS signal to be turned off.
A further security measure is the encryption of the P-code, yielding the P(Y) mode.
Thus, a PLGR is able to receive Coast Guard or other commercial broadcast correctables via the Radio Technical Commission Maritime protocol while tracking satellites and using the P(Y) code (an encrypted form of the P-code).
The encryption of the P-code, the P(Y) mode, provides a further security measure.