Squeak is an open, highly-portable Smalltalk implementation whose virtual machine is written entirely in Smalltalk, making it easy to. debug, analyze, and change. To achieve practical performance, a translator produces an equivalent C .program whose performance is comparable to commercial Smalltalks.Other noteworthy aspects of Squeak include: a compact object format that typically requires only a single word of overhead per object; a simple yet efficient incremental garbage collector for 32-bit direct pointers; efficient bulk-mutation of objects; extensions of BitBlt to handle color of any depth and antialiased image rotation and scaling; and real-time sound and music synthesis written entirely,@ Smalltalk.
Molecular nanotechnology is an engineering discipline in which the goal is to build devices and structures that have every atom in the proper place. By means of this general purpose material-processing technology it will be possible to build almost any rigid, covalently bonded structure. Identical parts will be truly identical, enabling energy conversion and computation systems to have extremely high performance and reliability. Assembly will be done by mechanosynthesis, the process of holding two reactive molecules in contact with each other in a controlled orientation. Synthesis will be done on nanoscale assembly lines called molecular mills, where systems of moving belts will press individual molecules together and catalyze 106 reactions/s per station. High-performance mechanical computers will use moving rods to block the motion of other rods. The most important physical limit will be radiation damage. Without redundancy, a subsystem lasting 100 years will be limited to 106 nm3.
The state of an imperative program-e.g., the values stored in global and local variables, objects' instance variables, and arrays-changes as its statements are executed. These changes, or side effects, are visible globally: when one part of the program modifies an object, every other part that holds a reference to the same object (either directly or indirectly) is also affected. This paper introduces worlds, a language construct that reifies the notion of program state, and enables programmers to control the scope of side effects. We investigate this idea as an extension of JavaScript, and provide examples that illustrate some of the interesting idioms that it makes possible.
LOOM (Large Object-Oriented Memory) is a virtual memory implemented in software that supports the Smalltalk-80(TM) programming language and environment on the Xerox Dorado computer. LOOM provides 8 billion bytes of secondary memory address space and is specifically designed to run on computers with a narrow word size (16-bit wide words). All storage is viewed as objects that contain fields. Objects may have an average size as small as I0 fields. LOOM swaps objects between primary and secondary memory, and addresses each of the two memories with a different sized object pointer. When objects are cached in primary memory, they are known only by their short pointers.On a narrow word size machine, the narrow object pointers in primary memory allow a program such as the Smalltalk-80 interpreter to enjoy a substantial speed advantage. Interesting design problems and solutions arise from the mapping between the two address spaces and the temporary nature of an object's short address. The paper explains why the unusual design choices in LOOM were made, and provides an interesting example of the process of designing an integrated virtual memory and storage management system.
LOOM (Large Object-Oriented Memory) is a virtual memory implemented in software that supports the Smalltalk-80(™) programming language and environment on the Xerox Dorado computer. LOOM provides 8 billion bytes of secondary memory address space and is specifically designed to run on computers with a narrow word size (16-bit wide words). All storage is viewed as objects that contain fields. Objects may have an average size as small as 10 fields. LOOM swaps objects between primary and secondary memory, and addresses each of the two memories with a different sized object pointer. When objects are cached in primary memory, they are known only by their short pointers. On a narrow word size machine, the narrow object pointers in primary memory allow a program such as the Smalltalk-80 interpreter to enjoy a substantial speed advantage. Interesting design problems and solutions arise from the mapping between the two address spaces and the temporary nature of an object's short address. The paper explains why the unusual design choices in LOOM were made, and provides an interesting example of the process of designing an integrated virtual memory and storage management system.
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