In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host,
peripheral device, disk sector, a memory cell or other logical or physical entity.
For software programs to save and retrieve stored data, each unit of data must have an address where it can be
individually located or else the program will be unable to find and manipulate the data. The number of address spaces available
will depend on the underlying address structure and these will usually be limited by the computer architecture being used.
Address spaces are created by combining enough uniquely identified qualifiers to make an address unambiguous (within a
particular address space). For a person's physical address, the address space would be a combination of locations, such as a
neighborhood, town, city, or country. Some elements of an address space may be the same– but if any element in the address is
different than addresses in said space will reference different entities. An example could be that there are multiple buildings
at the same address of "32 Main Street" but in different towns, demonstrating that different towns have different, although
similarly arranged, street address spaces.
An address space usually provides (or allows) a partitioning to several regions according to the mathematical structure
it has. In the case of total order, as for memory addresses, these are simply chunks. Some nested domains hierarchy appears in
the case of directed ordered tree as for the Domain Name System or a directory structure; this is similar to the hierarchical
design of postal addresses. In the Internet, for example, the Internet Assigned Numbers Authority (IANA) allocates ranges of IP
addresses to various registries in order to enable them to each manage their parts of the global Internet address space.
In computer security, a sandbox is a security mechanism for separating running programs, usually in an effort to mitigate system
failures or software vulnerabilities from spreading. It is often used to execute untested or untrusted programs or code, possibly from
unverified or untrusted third parties, suppliers, users or websites, without risking harm to the host machine or operating system.
A sandbox typically provides a tightly controlled set of resources for guest programs to run in, such as scratch space on disk and
memory. Network access, the ability to inspect the host system or read from input devices are usually disallowed or heavily restricted.
In the sense of providing a highly controlled environment, sandboxes may be seen as a specific example of virtualization.
Sandboxing is frequently used to test unverified programs that may contain a virus or other malicious code, without allowing the
software to harm the host device.
In computing, booting (or booting up) is the initialization of a computerized system. The system can be a computer or a computer
appliance. The booting process can be "hard", e.g., after electrical power to the CPU is switched from off to on (in order to diagnose
particular hardware errors), or "soft", when those power-on self-tests (POST) can be avoided. On some systems a soft boot may optionally
clear RAM to zero. Both hard and soft booting can be initiated by hardware such as a button press, or by software command. Booting is
complete when the normal, operative, runtime environment is attained.
A boot loader is a computer program that loads an operating system or some other system software for the computer after completion
of the power-on self-tests; it is the loader for the operating system itself. Within the hard reboot process, it runs after completion of
the self-tests, then loads and runs the software. A boot loader is loaded into main memory from persistent memory, such as a hard disk
drive or, in some older computers, from a medium such as punched cards, punched tape, or magnetic tape. The boot loader then loads and
executes the processes that finalize the boot. Like POST processes, the boot loader code comes from a "hard-wired" and persistent
location; if that location is too limited for some reason, that primary boot loader calls a second-stage boot loader or a secondary
On modern general purpose computers, the boot up process can take tens of seconds, or even minutes, and typically involves
performing a power-on self-test, locating and initializing peripheral devices, and then finding, loading and starting an operating
system. The process of hibernating or sleeping does not involve booting. Minimally, some embedded systems do not require a noticeable
boot sequence to begin functioning and when turned on may simply run operational programs that are stored in ROM. All computing systems
are state machines, and a reboot may be the only method to return to a designated zero-state from an unintended, locked state.
In addition to loading an operating system or stand-alone utility, the boot process can also load a storage dump program for
diagnosing problems in an operating system.
Boot is short for bootstrap or bootstrap load and derives from the phrase to pull oneself up by one's bootstraps. The usage
calls attention to the requirement that, if most software is loaded onto a computer by other software already running on the computer,
some mechanism must exist to load the initial software onto the computer. Early computers used a variety of ad-hoc methods to get a small
program into memory to solve this problem. The invention of read-only memory (ROM) of various types solved this paradox by allowing
computers to be shipped with a start up program that could not be erased. Growth in the capacity of ROM has allowed ever more elaborate
start up procedures to be implemented.
In computing, memory refers to the computer hardware devices involved to store information for immediate use in a computer; it is
synonymous with the term "primary storage". Computer memory operates at a high speed, for example random-access memory (RAM), as a
distinction from storage that provides slow-to-access program and data storage but offers higher capacities. If needed, contents of the
computer memory can be transferred to secondary storage, through a memory management technique called "virtual memory". An archaic
synonym for memory is store.
The term "memory", meaning "primary storage" or "main memory", is often associated with addressable semiconductor memory, i.e.
integrated circuits consisting of silicon-based transistors, used for example as primary storage but also other purposes in computers and
other digital electronic devices. There are two main kinds of semiconductor memory, volatile and non-volatile. Examples of non-volatile
memory are flash memory (used as secondary memory) and ROM, PROM, EPROM and EEPROM memory (used for storing firmware such as BIOS).
Examples of volatile memory are primary storage, which is typically dynamic random-access memory (DRAM), and fast CPU cache memory,
which is typically static random-access memory (SRAM) that is fast but energy-consuming, offering lower memory areal density than DRAM.
Most semiconductor memory is organized into memory cells or bistable flip-flops, each storing one bit (0 or 1). Flash memory
organization includes both one bit per memory cell and multiple bits per cell (called MLC, Multiple Level Cell). The memory cells are
grouped into words of fixed word length, for example 1, 2, 4, 8, 16, 32, 64 or 128 bit. Each word can be accessed by a binary address of
N bit, making it possible to store 2 raised by N words in the memory. This implies that processor registers normally are not considered as
memory, since they only store one word and do not include an addressing mechanism.
Typical secondary storage devices are hard disk drives and solid-state drives.
The graphical user interface (GUI), is a type of user interface that allows users to interact with electronic devices through
graphical icons and visual indicators such as secondary notation, instead of text-based user interfaces, typed command labels or text
navigation. GUIs were introduced in reaction to the perceived steep learning curve of command-line interfaces (CLIs), which require
commands to be typed on a computer keyboard.
The actions in a GUI are usually performed through direct manipulation of the graphical elements. Beyond computers, GUIs are
used in many handheld mobile devices such as MP3 players, portable media players, gaming devices, smartphones and smaller household,
office and industrial controls. The term GUI tends not to be applied to other lower-display resolution types of interfaces, such as
video games (where head-up display (HUD) is preferred), or not including flat screens, like volumetric displays because the term
is restricted to the scope of two-dimensional display screens able to describe generic information, in the tradition of the computer
science research at the Xerox Palo Alto Research Center.
In electronics, a logic gate is an idealized or physical device implementing a Boolean function; that is, it performs a logical
operation on one or more binary inputs and produces a single binary output. Depending on the context, the term may refer to an ideal
logic gate, one that has for instance zero rise time and unlimited fan-out, or it may refer to a non-ideal physical device (see Ideal
and real op-amps for comparison).
Logic gates are primarily implemented using diodes or transistors acting as electronic switches, but can also be constructed
using vacuum tubes, electromagnetic relays (relay logic), fluidic logic, pneumatic logic, optics, molecules, or even mechanical elements.
With amplification, logic gates can be cascaded in the same way that Boolean functions can be composed, allowing the construction of a
physical model of all of Boolean logic, and therefore, all of the algorithms and mathematics that can be described with Boolean logic.
Logic circuits include such devices as multiplexers, registers, arithmetic logic units (ALUs), and computer memory, all the way
up through complete microprocessors, which may contain more than 100 million gates. In modern practice, most gates are made from
field-effect transistors (FETs), particularly metal–oxide–semiconductor field-effect transistors (MOSFETs).
Compound logic gates AND-OR-Invert (AOI) and OR-AND-Invert (OAI) are often employed in circuit design because their construction
using MOSFETs is simpler and more efficient than the sum of the individual gates.
Multi-booting is the act of installing multiple operating systems on a computer, and being able to choose which one to boot. The
term dual-booting refers to the common configuration of specifically two operating systems. Multi-booting may require a custom boot
Multi-booting allows more than one operating system to reside on one computer, for example if you have a primary operating
system and an alternate system that you use less frequently. Another reason for multi-booting can be to investigate or test a new
operating system without switching completely. Multi-booting allows a new operating system to configure all applications needed, and
migrate data before removing the old operating system, if desired. A possible alternative to multi-booting is virtualization, where a
hypervisor is used to host one or more virtual machines running guest operating systems. Multi-booting is also useful in situations where
different software applications require different operating systems. A multi-boot configuration allows a user to use all of this
software on one computer. This is often accomplished by using a boot loader such as NTLDR, LILO, or GRUB which can boot more than one
operating system. Multi-booting is also used by software developers when multiple operating systems are required for development or
testing purposes. Having these systems on one machine is a way to reduce hardware costs.
In computer graphics, a raster graphics or bitmap image is a dot matrix data structure, representing a generally rectangular
grid of pixels, or points of color, viewable via a monitor, paper, or other display medium. Raster images are stored in image files with
A bitmap, a single-bit raster, corresponds bit-for-bit with an image displayed on a screen, generally in the same format used
for storage in the display's video memory, or maybe as a device-independent bitmap. A raster is technically characterized by the width
and height of the image in pixels and by the number of bits per pixel (or color depth, which determines the number of colors it can
The printing and prepress industries know raster graphics as contones (from "continuous tones"). The opposite to contones is
"line work", usually implemented as vector graphics in digital systems. Vector images can be rasterized, and raster images vectorized, by
software. In both cases some information is lost, although vectorizing can also restore some information back to machine readability, as
happens in optical character recognition.
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