|
C.mmp
The C.mmp was an early ''multiple instruction, multiple data'' ( MIMD) multiprocessor system developed at Carnegie Mellon University (CMU) by William Wulf (1971). The notation ''C.mmp'' came from the PMS notation of Gordon Bell and Allen Newell, where a central processing unit (CPU) was designated as ''C'', a variant was noted by the dot notation, and ''mmp'' stood for ''Multi-Mini-Processor''. , the machine is on display at CMU, in Wean Hall, on the ninth floor. Structure Sixteen Digital Equipment Corporation PDP-11 minicomputers were used as the processing elements, named Compute Modules (CMs) in the system. Each CM had a local memory of 8K and a local set of peripheral devices. One of the challenges was that a device was only available through its unique connected processor, so the input/output (I/O) system (designed by Roy Levien) hid the connectivity of the devices and routed the requests to the hosting processor. If a processor went down, the devices connected to its U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydra (operating System)
Hydra (stylized as HYDRA) is an early, discontinued, capability-based, object-oriented microkernel designed to support a wide range of possible operating systems to run on it.Wulf 74 pp. 337–345 Hydra was created as part of the C.mmp project at Carnegie-Mellon University in 1971. The name is based on the ancient Greek mythological creature the hydra. Hydra was designed to be modular and secure, and intended to be flexible enough for easy experimentation. The system was implemented in the programming language BLISS BLISS is a system programming language developed at Carnegie Mellon University (CMU) by W. A. Wulf, D. B. Russell, and A. N. Habermann around 1970. It was perhaps the best known system language until C debuted a few years later. Since then, C b .... References * * {{Operating-system-stub Capability systems Carnegie Mellon University software Microkernels Microkernel-based operating systems Object-oriented operating systems ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Wulf
William Allan Wulf (born December 8, 1939) is a computer scientist notable for his work in programming languages and compilers. Until June 2012, he was a university professor and the AT&T Professor of Engineering and Applied Sciences in the Department of Computer Science at the University of Virginia. Early life and education Born in Chicago, he attended the University of Illinois Urbana-Champaign, receiving a Bachelor of Science (B.S.) in engineering physics in 1961 and an Master of Science (M.S.) in electrical engineering in 1963. He then achieved the first Doctor of Philosophy (Ph.D.) in computer science from the University of Virginia in 1968. Career In 1970, while at Carnegie Mellon University (CMU), he designed the BLISS programming language and developed a groundbreaking optimizing compiler for it. From 1971–1975, as part of CMUs C.mmp project, he worked on an operating system (OS) microkernel named Hydra which is capability-based, object-oriented, and designed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capability-based Security
Capability-based security is a concept in the design of secure computing systems, one of the existing security models. A capability (known in some systems as a key) is a communicable, unforgeable token of authority. It refers to a value that references an object along with an associated set of access rights. A user program on a capability-based operating system must use a capability to access an object. Capability-based security refers to the principle of designing user programs such that they directly share capabilities with each other according to the principle of least privilege, and to the operating system infrastructure necessary to make such transactions efficient and secure. Capability-based security is to be contrasted with an approach that uses traditional UNIX permissions and Access Control Lists. Although most operating systems implement a facility which resembles capabilities, they typically do not provide enough support to allow for the exchange of capabilities ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PDP-11
The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of all models were sold, making it one of DEC's most successful product lines. The PDP-11 is considered by some experts to be the most popular minicomputer. The PDP-11 included a number of innovative features in its instruction set and additional general-purpose registers that made it much easier to program than earlier models in the PDP series. Further, the innovative Unibus system allowed external devices to be easily interfaced to the system using direct memory access, opening the system to a wide variety of peripherals. The PDP-11 replaced the PDP-8 in many real-time computing applications, although both product lines lived in parallel for more than 10 years. The ease of programming of the PDP-11 made it very popular for general-purpose computing use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Address
In computing, a physical address (also real address, or binary address), is a memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a ''particular'' storage cell of main memory, or a register of memory-mapped I/O device. Use by central processing unit In a computer supporting virtual memory, the term ''physical address'' is used mostly to differentiate from a '' virtual address''. In particular, in computers utilizing a memory management unit (MMU) to translate memory addresses, the virtual and physical addresses refer to an address before and after translation performed by the MMU, respectively. Unaligned addressing Depending upon its underlying computer architecture, the performance of a computer may be hindered by ''unaligned'' access to memory. For example, a 16-bit computer with a 16-bit memory data bus, such as Intel 8086, generally has less overhead if the access is aligned to an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multi-user Software
Multi-user software is computer software that allows access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving the CPU idle while it waits for I/O operations to complete. However, the term " multitasking" is more common in this context. An example is a Unix or Unix-like system where multiple remote users have access (such as via a serial port or Secure Shell) to the Unix shell prompt at the same time. Another example uses multiple X Window sessions spread across multiple terminals powered by a single machine - this is an example of the use of thin client. Similar functions were also available in a variety of non-Unix-like operating systems, such as Multics, VM/CMS, OpenVMS, MP/M, Concurrent CP/M, Concurrent DOS, FlexOS, Multiuser DOS, REAL/32, OASIS, THEOS, PC-MOS, TSX-32 and VM/386. Some multi-user operating systems such as Windows versions fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object-oriented Programming
Object-oriented programming (OOP) is a programming paradigm based on the concept of " objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of procedures (often known as '' methods''). A common feature of objects is that procedures (or methods) are attached to them and can access and modify the object's data fields. In this brand of OOP, there is usually a special name such as or used to refer to the current object. In OOP, computer programs are designed by making them out of objects that interact with one another. OOP languages are diverse, but the most popular ones are class-based, meaning that objects are instances of classes, which also determine their types. Many of the most widely used programming languages (such as C++, Java, Python, etc.) are multi-paradigm and they support object-oriented programming to a greater or lesser degree, typically in combination with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trap (computing)
In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, the processor will suspend its current activities, save its state, and execute a function called an ''interrupt handler'' (or an ''interrupt service routine'', ISR) to deal with the event. This interruption is often temporary, allowing the software to resume normal activities after the interrupt handler finishes, although the interrupt could instead indicate a fatal error. Interrupts are commonly used by hardware devices to indicate electronic or physical state changes that require time-sensitive attention. Interrupts are also commonly used to implement computer multitasking, especially in real-time computing. Systems that use interrupts in these ways are said to be interrupt-driven. Types Interrupt signals may be issued in response to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microcode
In processor design, microcode (μcode) is a technique that interposes a layer of computer organization between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. Microcode is a layer of hardware-level instructions that implement higher-level machine code instructions or internal finite-state machine sequencing in many digital processing elements. Microcode is used in general-purpose central processing units, although in current desktop CPUs, it is only a fallback path for cases that the faster hardwired control unit cannot handle. Microcode typically resides in special high-speed memory and translates machine instructions, state machine data, or other input into sequences of detailed circuit-level operations. It separates the machine instructions from the underlying electronics so that instructions can be designed and altered more freely. It also facilitates the building of complex multi-step instructions, whil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backplane
A backplane (or "backplane system") is a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used as a backbone to connect several printed circuit boards together to make up a complete computer system. Backplanes commonly use a printed circuit board, but wire-wrapped backplanes have also been used in minicomputers and high-reliability applications. A backplane is generally differentiated from a motherboard by the lack of on-board processing and storage elements. A backplane uses plug-in cards for storage and processing. Usage Early microcomputer systems like the Altair 8800 used a backplane for the processor and expansion cards. Backplanes are normally used in preference to cables because of their greater reliability. In a cabled system, the cables need to be flexed every time that a card is added or removed from the system; this flexing eve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wire Wrap
Wire wrap is an electronic component assembly technique that was invented to wire telephone crossbar switches, and later adapted to construct electronic circuit boards. Electronic components mounted on an insulating board are interconnected by lengths of insulated wire run between their terminals, with the connections made by wrapping several turns of uninsulated sections of the wire around a component lead or a socket pin. Wires can be wrapped by hand or by machine, and can be hand-modified afterwards. It was popular for large-scale manufacturing in the 1960s and early 1970s, and continues today to be used for short runs and prototypes. The method eliminates the design and fabrication of a printed circuit board. Wire wrapping is unusual among other prototyping technologies since it allows for complex assemblies to be produced by automated equipment, but then easily repaired or modified by hand. Wire wrap construction can produce assemblies which are more reliable than printe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> PDP-11")
