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Automatic Reference Counting
Automatic Reference Counting (ARC) is a memory management feature of the Clang compiler providing automatic reference counting for the Objective-C and Swift (programming language), Swift programming languages. At compile time, it inserts into the object code object-oriented programming#Dynamic dispatch/message passing, messages retain and release which increase and decrease the reference count at run time, marking for deallocation those object (computer science), objects when the number of references to them reaches zero. ARC differs from tracing garbage collection in that there is no background process that deallocates the objects asynchronously at runtime. Unlike tracing garbage collection, ARC does not handle reference counting#reference cycle, reference cycles automatically. This means that as long as there are "strong" references to an object, it will not be deallocated. Strong cross-references can accordingly create Deadlock (computer science), deadlocks and memory leaks. It i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Management
Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of Resource management (computing), resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when no longer needed. This is critical to any advanced computer system where more than a single Process (computing), process might be underway at any time. Several methods have been devised that increase the effectiveness of memory management. Virtual memory systems separate the memory addresses used by a process from actual physical addresses, allowing separation of processes and increasing the size of the virtual address space beyond the available amount of Random-access memory, RAM using paging or swapping to secondary storage. The quality of the virtual memory manager can have an extensive effect on overall system C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deadlock (computer Science)
In concurrent computing, deadlock is any situation in which no member of some group of entities can proceed because each waits for another member, including itself, to take action, such as sending a message or, more commonly, releasing a lock. Deadlocks are a common problem in multiprocessing systems, parallel computing, and distributed systems, because in these contexts systems often use software or hardware locks to arbitrate shared resources and implement process synchronization. In an operating system, a deadlock occurs when a process or thread enters a waiting state because a requested system resource is held by another waiting process, which in turn is waiting for another resource held by another waiting process. If a process remains indefinitely unable to change its state because resources requested by it are being used by another process that itself is waiting, then the system is said to be in a deadlock. In a communications system, deadlocks occur mainly due to loss ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Runtime Library
A runtime library is a library that provides access to the runtime environment that is available to a computer program tailored to the host platform. A runtime environment implements the execution model as required for a development environment such as a particular programming language. A runtime library may provide basic program facilities such as for memory management and exception handling. A runtime library is an artifact of the design of the toolchain used to build the program not inherently required by the host operating system or the programming language in which the program is written. The toolset is designed to abstract aspects of the host platform often to simplify tool development. The toolchain builds a program to depend on a runtime library and to use it while the program is running at program run-time. The runtime library may directly implement runtime behavior, but often it is a thin wrapper on top of operating system facilities. For example, some langua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OS X Mountain Lion
OS X Mountain Lion (version 10.8) is the ninth major release of macOS, Apple Inc.'s desktop and server operating system for Macintosh computers. OS X Mountain Lion was released on July 25, 2012, for purchase and download through the Mac App Store, as part of a switch to releasing OS X versions online and every year, rather than every two years. Named to signify its status as a refinement of the previous OS X version, Lion, Apple's stated aims in developing Mountain Lion were to allow users to more easily manage and synchronise content between multiple Apple devices and to make the operating system more familiar. The operating system gained the new malware-blocking system Gatekeeper and integration with Apple's online Game Center and iCloud services, while the Safari web browser was updated to version 6. As on iOS, Notes and Reminders became full applications, separate from Mail and Calendar, while the iChat application was replaced with a version of iOS's Messages. Mount ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IOS 5
iOS 5 is the iOS version history, fifth major release of the iOS mobile operating system developed by Apple Inc., being the successor to iOS 4. It was announced at the company's Worldwide Developers Conference on June 6, 2011, and was released on October 12, 2011. It was succeeded by iOS 6 on September 19, 2012. iOS 5 revamped notifications, adding temporary banners that appear at the top of the screen and introducing the Notification Center, a central location for all recent notifications. iOS 5 also added iCloud, Apple's cloud storage service for synchronization of content and data across iCloud-enabled devices, and iMessage, Apple's instant messaging service. For the first time, software updates could be installed wirelessly, without requiring a computer and iTunes. iOS 5 also featured deep integration with Twitter, introduced multitasking gestures on iPads, and added an easily accessible camera shortcut from the lock screen. iOS 5 was the subject of criticism for iPhone 4s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mac OS X Lion
OS X Lion, also known as Mac OS X Lion, (version 10.7) is the eighth major release of macOS, Apple's desktop and server operating system for Mac computers. A preview of OS X 10.7 Lion was publicly shown at the "Back to the Mac" Apple Special Event on October 20, 2010. It brought many developments made in Apple's iOS, such as an easily navigable display of installed applications, to the Mac, and includes support for the Mac App Store, as introduced in Mac OS X 10.6 Snow Leopard version 10.6.6. On February 24, 2011, the first developer's preview of Lion (11A390) was released to subscribers to the Apple Developer program. Other developer previews were subsequently released, with Lion Preview 4 (11A480b) being released at WWDC 2011. Lion was released to manufacturing on July 1, 2011, followed by its final release via the Mac App Store on July 20, 2011. Apple reported over one million Lion sales on the first day of its release. , OS X Lion had sold over six million copies wo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IOS 4
iOS 4 is the fourth major release of the iOS mobile operating system developed by Apple Inc., being the successor to iPhone OS 3. It was announced at the Apple Special Event on April 8, 2010, and released on June 21, 2010. iOS 4 was the first version branded as "iOS" rather than "iPhone OS", due to the release of the iPad. It was succeeded by iOS 5 on October 12, 2011. iOS 4 introduced many features that have since become commonplace, such as folders on the home screen, significantly increasing the number of apps that can be displayed. Support for home screen wallpapers on the iPhone was also added, although limited to newer devices due to animation performance requirements. The operating system also added a multitasking feature, letting apps dealing with Internet calling, location and audio playback function in the background, whereas a similar but more restricted "Fast App Switching" technology enabled any app to be left inactive in the background while users switch to othe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mac OS X Snow Leopard
Mac OS X Snow Leopard (version 10.6) (also referred to as OS X Snow Leopard) is the seventh major release of macOS, Apple's desktop and server operating system for Macintosh computers. Snow Leopard was publicly unveiled on June 8, 2009, at Apple’s Worldwide Developers Conference. On August 28, 2009, it was released worldwide, and was made available for purchase from Apple's website and retail stores at the price of $29 USD for a single-user license. As a result of its low price, initial sales of Snow Leopard were significantly higher than its predecessors, which had prices starting at $129 USD. The release of Snow Leopard came nearly two years after the launch of Mac OS X Leopard, the second longest time span between successive Mac OS X releases (the time span between Tiger and Leopard was the longest). The goals of Snow Leopard were improved performance, greater efficiency and the reduction of its overall memory footprint, unlike previous versions of Mac OS X which focused ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MacOS
macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. Within the market of Desktop computer, desktop and laptop computers, it is the Usage share of operating systems#Desktop and laptop computers, second most widely used desktop OS, after Microsoft Windows and ahead of all Linux distributions, including ChromeOS and SteamOS. , the most recent release of macOS is MacOS Sequoia, macOS 15 Sequoia, the 21st major version of macOS. Mac OS X succeeded classic Mac OS, the primary Mac operating systems, Macintosh operating system from 1984 to 2001. Its underlying architecture came from NeXT's NeXTSTEP, as a result of NeXT#1997–2006: Acquisition by Apple, Apple's acquisition of NeXT, which also brought Steve Jobs back to Apple. The first desktop version, Mac OS X 10.0, was released on March 24, 2001. Mac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apple Inc
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 leavin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weak Reference
In computer programming, a weak reference is a reference that does not protect the referenced object from collection by a garbage collector, unlike a strong reference. An object referenced ''only'' by weak references – meaning "every chain of references that reaches the object includes at least one weak reference as a link" – is considered '' weakly reachable,'' and can be treated as unreachable and so may be collected at any time. Some garbage-collected languages feature or support various levels of weak references, such as C#, Lua, Java, Lisp, OCaml, MATLAB, Perl, Python and PHP since the version 7.4. Uses Weak references have a number of common uses. When using reference counting garbage collection, weak references can break reference cycles, by using a weak reference for a link in the cycle. When one has an associative array (mapping, hash map) whose keys are (references to) objects, for example to hold auxiliary data about objects, using weak references for the keys a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Leak
In computer science, a memory leak is a type of resource leak that occurs when a computer program incorrectly manages memory allocations in a way that memory which is no longer needed is not released. A memory leak may also happen when an object is stored in memory but cannot be accessed by the running code (i.e. unreachable memory). A memory leak has symptoms similar to a number of other problems and generally can only be diagnosed by a programmer with access to the program's source code. A related concept is the "space leak", which is when a program consumes excessive memory but does eventually release it. Because they can exhaust available system memory as an application runs, memory leaks are often the cause of or a contributing factor to software aging. Effects Minor leaks If a program has a memory leak and its memory usage is steadily increasing, there will not usually be an immediate symptom. In modern operating systems, normal memory used by an application is releas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
