1 edition of Abstraction in the INTEL iAPX-432 prototype systems implementation language found in the catalog.
Abstraction in the INTEL iAPX-432 prototype systems implementation language
Bruce J. MacLennan
This report describes the abstraction mechanism of a prototype systems implementaiton language for Intel"s iAPX-432 microprocessor. Full exploitation of the 432"s facilities places many demands on a language intended for systems implementation. The 432 is a capability-based machine, with hardware-enforced typing of large objects, dynamically instantiated domains (i.e., packages), hardware-enforced information information hiding (seals), and hardware-supported, software-defined access-rights (trademarks). The prototype language"s support for these facilities is described in this project.
|Statement||Bruce J. MacLennan|
|Contributions||Naval Postgraduate School (U.S.)|
|The Physical Object|
|Pagination||26 p. ;|
|Number of Pages||26|
Some languages have special support for mixinsthough in any language with multiple inheritance, a mixin is simply a class that does not represent an is-a-type-of relationship. Its dominance was further enhanced by the rising popularity of graphical user interfaces, which rely heavily upon object-oriented programming techniques. Objects and Classes Languages that support object-oriented programming typically use inheritance for code reuse and extensibility in the form of either classes or prototypes. Experimentation with various extensions to Lisp such as LOOPS and Flavors introducing multiple inheritance and mixins eventually led to the Common Lisp Object Systemwhich integrates functional programming and object-oriented programming and allows extension via a Meta-object protocol. The execution unit the third stage of the pipeline is made up of two independent subprocessors, the data manipulation unit DMU and the reference generation unit RGU. Those that use classes support two main concepts: Classes — the definitions for the data format and available procedures for a given type or class of object; may also contain data and procedures known as class methods themselves, i.
This allows classes to be arranged in a hierarchy that represents "is-a-type-of" relationships. So bark is one of Lassie's methods. Timmy, Lassie's friend, however, does not need to know exactly how she barks. Experimentation with various extensions to Lisp such as LOOPS and Flavors introducing multiple inheritance and mixins eventually led to the Common Lisp Object System, which integrates functional programming and object-oriented programming and allows extension via a Meta-object protocol. This intuition is unfortunately false in most OOP languages, in particular in all those that allow mutable objects. How this is implemented varies from language to language, but most OOP languages support at least some level of overloading polymorphism.
A class should typically be recognizable to a non-programmer familiar with the problem domain, meaning that the characteristics of the class should make sense in context. A larger issue was the capability architecture needed large associative caches to run efficiently, but the chips had no room left for that. Adding these features to languages that were not initially designed for them often led to problems with compatibility and maintainability of code. Modules that try to access segments that are not in its access descriptors produce a fault III,
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The cache was too small; it improved performance but not enough to compensate for the slow memory accesses caused by error checking and other similar problems V.
OOP in a network protocol[ edit ] The messages that flow between computers to request services in a client-server environment can be designed as the linearizations of objects defined by class objects known to both the client and the server.
Simula not only introduced the notion of classes, but also of instances of classes, which is probably the first explicit use of those notions.
The segment descriptors and address descriptors as well as the addresses of commonly accessed items like the segment table that were most recently used are all stored on the chip III, Methods may also be designed public, private, or intermediate levels such as protected which allows access from the same class and its subclasses, but not objects of a different class.
The lack of user accessible registers means that context switches are fairly efficient.
Matching real world OOP can be used to translate from real-world phenomena to program elements and vice versa. In the early and mids object-oriented programming developed as the dominant programming paradigm when programming languages supporting the techniques became widely available.
InKristen Nygaard initiated a project for a simulation language at the Norwegian Computing Center, based on his previous use of the Monte Carlo simulation and his work to conceptualise real-world systems.
The authors hold that responsibility-driven design is preferable. More recently, a number of languages have emerged that are primarily object-oriented, but that are also compatible with procedural methodology. Encapsulation[ edit ] If a class disallows calling code from accessing internal object data and forces access through methods only, this is a strong form of abstraction or information hiding known as encapsulation.
It was created for making simulation programsin which what came to be called objects were the most important information representation. A method call is also known as message passing. This leads to the following terms: Class variables - belong to the class as a whole; there is only one copy of each one Instance variables or attributes - data that belongs to individual objects; every object has its own copy of each one Member variables - refers to both the class and instance variables that are defined by a particular class Class methods - belong to the class as a whole and have access only to class variables and inputs from the procedure call Instance methods - belong to individual objects, and have access to instance variables for the specific object they are called on, inputs, and class variables Objects are accessed somewhat like variables with complex internal structure, and in many languages are effectively pointersserving as actual references to a single instance of said object in memory within a heap or stack.
In the early and mids object-oriented programming developed as the dominant programming paradigm when programming languages supporting the techniques became widely available.
Unsourced material may be challenged and removed. The technology focuses on data rather than processes, with programs composed of self-sufficient modules "classes"each instance of which "objects" contains all the information needed to manipulate its own data structure "members".
It is a programming methodology that gives modular component development while at the same time being very efficient. This facilitates code refactoring, for example allowing the author of the class to change how objects of that class represent their data internally without changing any external code as long as "public" method calls work the same way.
A Dog has fur; Lassie has brown-and-white fur. In this case, Lassie would be an instance of the Collie subclass. Every object has one prototype link and only one. A class should typically be recognizable to a non-programmer familiar with the problem domain, meaning that the characteristics of the class should make sense in context.
Pierce and some other researchers view as futile any attempt to distill OOP to a minimal set of features. Composition, inheritance, and delegation[ edit ] Objects can contain other objects in their instance variables; this is known as object composition.
Each copy of the bank account object would be alike in the methods it offers for manipulating or reading its data, but the data inside each object would differ reflecting the different history of each account.
For example, the Dog class has a bark method. Modula-2 included both, and their succeeding design, Oberonincluded a distinctive approach to object orientation, classes, and such. Abstraction is also achieved through Composition. Delegation is another language feature that can be used as an alternative to inheritance.
Simula thus introduced the class and subclass hierarchy, and the possibility of generating objects from these classes. Terminology invoking "objects" and "oriented" in the modern sense of object-oriented programming made its first appearance at MIT in the late s and early s.
Languages with most of the features of objects classes, methods, inheritance, reusabilitybut in a distinctly original form.Object-oriented programming (OOP) is a programming paradigm based on the concept of objects, which can contain data, in the form of fields (often known as attributes or properties), and code, in the form of procedures (often known as methods).
A feature of objects is an object's procedures that can. Hints for Computer System Design. Butler W. Lampson Computer Science Laboratory Xerox Palo Alto Research Center Palo Alto, CA Abstract. Studying the design and implementation of a number of computer has led to some general hints for system design.
Object-oriented programming (OOP) is a programming paradigm that represents concepts as "objects" that have data fields (attributes that describe the object) and associated procedures known as sylvaindez.coms, which are usually instances of classes, are used to interact with one another to design applications and computer programs.C++ and Java are examples of object oriented programming.
For example, the languages of the Argus and Emerald systems adapted object-oriented programming to distributed systems. The s also brought advances in programming language implementation.
The RISC movement in computer architecture postulated that hardware should be designed for compilers rather than for human assembly programmers. Sep 10, · Intel even got “into Ada” by making an Ada oriented, 32 bit processor, the iAPX, that had instructions to validate integer ranges, a “big deal” back then, since many complained about.
The displaywriter group had done a lot of code in PL.8 (the original risc programming language from the 70s) and in the morph to PC/RT built something called the VRM (written in pl.8) with a virtual machine abstraction layer.