O-code machine
Encyclopedia
The O-code machine is a virtual machine
that was developed by Martin Richards in the late 1960s to give machine independence to BCPL
, the low-level forerunner to C
and C++
. The concept behind the O-Code machine was to create O-code output (O stands for Object) through the BCPL compiler. The O-code was then either interpreted or, more normally, compiled to machine specific code. This idea was used in later compilers, such as p-code
for some Pascal
compilers and the JVM
code for Java
compilers. O-code allowed Richards to separate general compilation issues from machine specific implementation issues when writing the BCPL compiler. Its use in the BCPL compiler made the compiler easy to port and as a result BCPL quickly became available for many machines.
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
that was developed by Martin Richards in the late 1960s to give machine independence to BCPL
BCPL
BCPL is a procedural, imperative, and structured computer programming language designed by Martin Richards of the University of Cambridge in 1966.- Design :...
, the low-level forerunner to C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
and C++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...
. The concept behind the O-Code machine was to create O-code output (O stands for Object) through the BCPL compiler. The O-code was then either interpreted or, more normally, compiled to machine specific code. This idea was used in later compilers, such as p-code
P-Code machine
In computer programming, a p-code machine, or portable code machine is a virtual machine designed to execute p-code...
for some Pascal
Pascal (programming language)
Pascal is an influential imperative and procedural programming language, designed in 1968/9 and published in 1970 by Niklaus Wirth as a small and efficient language intended to encourage good programming practices using structured programming and data structuring.A derivative known as Object Pascal...
compilers and the JVM
Java Virtual Machine
A Java virtual machine is a virtual machine capable of executing Java bytecode. It is the code execution component of the Java software platform. Sun Microsystems stated that there are over 4.5 billion JVM-enabled devices.-Overview:...
code for Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
compilers. O-code allowed Richards to separate general compilation issues from machine specific implementation issues when writing the BCPL compiler. Its use in the BCPL compiler made the compiler easy to port and as a result BCPL quickly became available for many machines.
External links
- The BCPL Cintcode System and Cintpos User Guide by Martin Richards (672KB pdf format)
- Bootstrapping the BCPL Compiler using INTCODE - definitive document explaining the history of OCODE and INTCODE, by Martin Richards.