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Base And Bounds
In computing base and bounds refers to a simple form of virtual memory where access to computer memory is controlled by one or a small number of sets of processor registers called ''base and bounds registers''. In its simplest form each user process is assigned a single contiguous segment of main memory. The operating system loads the physical address of this segment into a ''base register'' and its size into a ''bound register''. ''Virtual'' addresses seen by the program are added to the contents of the base register to generate the ''physical address''. The address is checked against the contents of the bounds register to prevent a process from accessing memory beyond its assigned segment. The operating system is not constrained by the hardware and can access all of physical memory. This technique protects memory used by one process against access or modification by another. By itself it does not protect memory from erroneous access by the owning process. It also allows program ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and software. Computing has scientific, engineering, mathematical, technological, and social aspects. Major computing disciplines include computer engineering, computer science, cybersecurity, data science, information systems, information technology, and software engineering. The term ''computing'' is also synonymous with counting and calculation, calculating. In earlier times, it was used in reference to the action performed by Mechanical computer, mechanical computing machines, and before that, to Computer (occupation), human computers. History The history of computing is longer than the history of computing hardware and includes the history of methods intended for pen and paper (or for chalk and slate) with or without the aid of tables. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PDP-10
Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, especially as the TOPS-10 operating system became widely used. The PDP-10's architecture is almost identical to that of DEC's earlier PDP-6, sharing the same 36-bit Word (computer architecture), word length and slightly extending the instruction set. The main difference was a greatly improved hardware implementation. Some aspects of the instruction set are unusual, most notably the ''byte'' instructions, which operate on bit fields of any size from 1 to 36 bits inclusive, according to the general definition of a byte as ''a contiguous sequence of a fixed number of bits''. The PDP-10 was found in many university computing facilities and research labs during the 1970s, the most notable being Harvard University's Aiken Computation Laboratory, Mass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Management Unit
A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit that examines all references to computer memory, memory, and translates the memory addresses being referenced, known as virtual memory addresses, into physical addresses in main memory. In modern systems, programs generally have addresses that access the theoretical maximum memory of the computer architecture, 32 or 64 bits. The MMU maps the addresses from each program into separate areas in physical memory, which is generally much smaller than the theoretical maximum. This is possible because programs rarely use large amounts of memory at any one time. Most modern operating systems (OS) work in concert with an MMU to provide virtual memory (VM) support. The MMU tracks memory use in fixed-size blocks known as ''pages''. If a program refers to a location in a page that is not in physical memory, the MMU sends an interrupt to the operating system. The OS selects a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Management (operating Systems)
In operating systems, memory management is the function responsible for managing the computer's primary memory. The memory management function keeps track of the status of each memory location, either ''allocated'' or ''free''. It determines how memory is allocated among competing processes, deciding which gets memory, when they receive it, and how much they are allowed. When memory is allocated it determines which memory locations will be assigned. It tracks when memory is freed or ''unallocated'' and updates the status. This is distinct from application memory management, which is how a process manages the memory assigned to it by the operating system. Memory management techniques Single contiguous allocation ''Single allocation'' is the simplest memory management technique. All the computer's memory, usually with the exception of a small portion reserved for the operating system, is available to a single application. MS-DOS is an example of a system that allocates memory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoshop
Adobe Photoshop is a raster graphics editor developed and published by Adobe for Windows and macOS. It was created in 1987 by Thomas and John Knoll. It is the most used tool for professional digital art, especially in raster graphics editing, and its name has become genericised as a verb (e.g. "to photoshop an image", " photoshopping", and " photoshop contest") although Adobe disapproves of such use. Photoshop can edit and compose raster images in multiple layers and supports masks, alpha compositing and several color models. Photoshop uses its own PSD and PSB file formats to support these features. In addition to raster graphics, Photoshop has limited abilities to edit or render text and vector graphics (especially through clipping path for the latter), as well as 3D graphics and video. Its feature set can be expanded by plug-ins; programs developed and distributed independently of Photoshop that run inside it and offer new or enhanced features. Photoshop's naming sch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resource Fork
A resource fork is a fork of a file on Apple's classic Mac OS operating system that is used to store structured data. It is one of the two forks of a file, along with the data fork, which stores data that the operating system treats as unstructured. Resource fork capability has been carried over to the modern macOS for compatibility. A resource fork stores information in a specific form, containing details such as icon bitmaps, the shapes of windows, definitions of menus and their contents, and application code ( machine code). For example, a word processing file might store its text in the data fork, while storing any embedded images in the same file's resource fork. The resource fork is used mostly by executables, but any file can have a resource fork. In a 1986 technical note, Apple strongly recommended that developers do not put general data into the resource fork of a file. According to Apple, there are parts of the system software that rely on resource forks having only v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MultiFinder
MultiFinder is an extension for the Apple Macintosh's classic Mac OS, introduced on August 11, 1987 and included with System Software 5. It adds cooperative multitasking of several applications at once – a great improvement over the previous Macintosh systems, which can only run one application at a time. With the advent of System 7, MultiFinder became a standard integrated part of the operating system and remained so until the introduction of Mac OS X. History Background The first Macintosh was released in 1984, and Apple's developers made an early decision that the machine's 128 KB of RAM was so limited that they must abandon the application multitasking functionality that Apple had developed for the Lisa. As the successive Macintosh hardware models were released with much more RAM being the key feature, new programming techniques were developed as workarounds to allow users to run concurrent applications. Desk Accessories became a staple through the lifespan of System ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apple Computer
Apple Inc. is an American multinational corporation and technology company headquartered in Cupertino, California, in Silicon Valley. It is best known for its consumer electronics, software, and services. Founded in 1976 as Apple Computer Company by Steve Jobs, Steve Wozniak and Ronald Wayne, the company was incorporated by Jobs and Wozniak as Apple Computer, Inc. the following year. It was renamed Apple Inc. in 2007 as the company had expanded its focus from computers to consumer electronics. Apple is the largest technology company by revenue, with billion in the 2024 fiscal year. The company was founded to produce and market Wozniak's Apple I personal computer. Its second computer, the Apple II, became a best seller as one of the first mass-produced microcomputers. Apple introduced the Lisa in 1983 and the Macintosh in 1984, as some of the first computers to use a graphical user interface and a mouse. By 1985, internal company problems led to Jobs leaving to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UNIVAC 1100/2200 Series
The UNIVAC 1100/2200 series is a series of compatible 36-bit computer systems, beginning with the UNIVAC 1107 in 1962, initially made by Sperry Rand. The series continues to be supported today by Unisys Corporation as the ClearPath Dorado Series. The solid-state 1107 model number was in the same sequence as the earlier vacuum-tube computers, but the early computers were not compatible with their solid-state successors. Architecture Data formats * Fixed-point, either integer or fraction **Whole word – 36-bit (ones' complement) **Half word – two 18-bit fields per word (unsigned or ones' complement) **Third word – three 12-bit fields per word (ones' complement) **Quarter word – four 9-bit fields per word (unsigned) **Sixth word – six 6-bit fields per word (unsigned) * Floating point **Single precision – 36 bits: sign bit, 8-bit characteristic, 27-bit mantissa **Double precision – 72 bits: sign bit, 11-bit characteristic, 60-bit mantissa *Alphanumeric ** FIELDATA � ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Memory
In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very large (main) memory". The computer's operating system, using a combination of hardware and software, maps memory addresses used by a program, called '' virtual addresses'', into ''physical addresses'' in computer memory. Main storage, as seen by a process or task, appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit (MMU), automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities, utilizing, e.g., disk storage, to provide a virtual address space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relocation (computing)
In software development, relocation is the process of assigning load addresses for position-dependent code and data of a program and adjusting the code and data to reflect the assigned addresses. A linker usually performs relocation in conjunction with ''symbol resolution'', the process of searching files and libraries to replace symbolic references or names of libraries with actual usable addresses in memory before running a program. Relocation is typically done by the linker at link time, but it can also be done at load time by a relocating loader, or at run time by the running program itself. Segmentation Object files are typically segmented into various memory segment or section types. Example segment types include code segment (.text), initialized data segment (.data), uninitialized data segment (.bss), or others as established by the programmer, such as common segments, or named static segments. Relocation table The relocation table is a list of address ... [...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 even ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
