Misplaced Pages

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76-571: With the introduction of Mac OS X 10.6 , Apple dropped support for formatting or writing HFS disks and images , which remained supported as read-only volumes until macOS 10.15 . Starting with macOS 10.15, HFS disks can no longer be read. Apple introduced HFS in September 1985, specifically to support Apple's first hard disk drive for the Macintosh, replacing the Macintosh File System (MFS),

152-493: A C -based programming language with a structure that is already familiar to Mac OS X programmers, who can use Xcode developer tools to adapt their programs to work with OpenCL. Only the most process intensive parts of the application need to be written in OpenCL C without affecting the rest of the code. OpenCL is an open standard that has been supported by AMD , Intel , and Nvidia ; it is maintained by Khronos Group . It serves

228-435: A swap file or swap partition is a way for the operating system to provide more memory than is physically available by keeping portions of the primary memory in secondary storage . While multitasking and memory swapping are two completely unrelated techniques, they are very often used together, as swapping memory allows more tasks to be loaded at the same time. Typically, a multitasking system allows another process to run when

304-511: A 64-bit kernel by default; newer iMac and MacBook Pro machines can run a 64-bit kernel, but will not do so by default. Users wishing to use the 64-bit kernel on those machines must hold down the numbers 6 and 4 on the keyboard while booting to get the 64-bit kernel to load. A change to the com.apple.Boot.plist will also enable users with compatible computers to permanently boot into 64-bit for those wishing to do so. Stuart Harris, software product marketing manager at Apple Australia, said, "For

380-652: A Macintosh computer model behind: the original 128K Macintosh , which lacked sufficient memory to load the HFS code and was promptly discontinued. In 1998, Apple introduced HFS Plus to address inefficient allocation of disk space in HFS and to add other improvements. HFS Plus is still supported by current versions of Mac OS, but starting with Mac OS X , an HFS volume cannot be used for booting , and beginning with Mac OS X 10.6 (Snow Leopard), HFS volumes are read-only and cannot be created or updated. In macOS Sierra (10.12), Apple's release notes state that "The HFS Standard filesystem

456-461: A Program Distributor feeding up to twenty-five autonomous processing units with code and data, and allowing concurrent operation of multiple clusters. Another such computer was the LEO III , first released in 1961. During batch processing , several different programs were loaded in the computer memory, and the first one began to run. When the first program reached an instruction waiting for a peripheral,

532-476: A bug that frequently prevented DNS queries from returning IPv6 addresses . This was resolved in 10.6.8. At the WWDC in 2009, Apple stated that Snow Leopard features no new major visual changes. Instead, the release focuses on refining the operating system to enable better performance. OSNews reported that Mac OS X Snow Leopard was well received by critics. Engadget reviewed Snow Leopard and pointed out that

608-603: A clean install. But he complained of slowness even after his clean install. He wrote, "I ended up downgrading back to OSX 10.5.8" then he concluded by writing, "I might try to do it again but it won't be till Apple releases at least 2 major fix updates. If you want to roll the dice and try, go ahead... your upgrade might work, however, random installs not working is not good for me. Lesson learned --- I'll wait." The single-user upgrade and Family Pack units of Snow Leopard ranked 1 and 2 respectively on Amazon.com 's software bestseller charts when Apple announced it would release it within

684-465: A computer's memory, allowing the CPU to switch between them swiftly. This optimizes CPU utilization by keeping it engaged with the execution of tasks, particularly useful when one program is waiting for I/O operations to complete. The Bull Gamma 60 , initially designed in 1957 and first released in 1960, was the first computer designed with multiprogramming in mind. Its architecture featured a central memory and

760-630: A discounted price through its "up-to-date" program, provided that customers' orders were faxed or postmarked by December 26, 2009. The standalone retail version of Snow Leopard is marketed as being restricted to users of Mac OS X Leopard , while the recommended upgrade path from Apple for Mac OS X Tiger is through the " Mac Box Set ", which includes Mac OS X Snow Leopard and the current versions of iLife and iWork . There are three licenses available. These licenses differ in their requirements for pre-installed versions of Mac OS X: If you have purchased an Upgrade for Mac OS X Leopard license, then subject to

836-534: A list of applications with known compatibility issues with Snow Leopard. Printer and scanner drivers used by previous versions of Mac OS X are not compatible with Snow Leopard and will be replaced during Snow Leopard installation. Since the initial release of Snow Leopard many manufacturers have provided compatible drivers that are available via Software Update. If a native driver is not available Snow Leopard also includes CUPS and Gutenprint open source drivers that may provide limited functionality. 10.6.0 introduced

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912-542: A number of design features with MFS that were not available in other file systems of the time (such as DOS 's FAT ). Files could have multiple forks (normally a data and a resource fork ), which allowed the main data of the file to be stored separately from resources such as icons that might need to be localized. Files were referenced with unique file IDs rather than file names, and file names could be up to 31 characters long. However, MFS had been optimized to be used on very small and slow media, namely floppy disks , so HFS

988-523: A program will run in a timely manner. Indeed, the first program may very well run for hours without needing access to a peripheral. As there were no users waiting at an interactive terminal, this was no problem: users handed in a deck of punched cards to an operator, and came back a few hours later for printed results. Multiprogramming greatly reduced wait times when multiple batches were being processed. Early multitasking systems used applications that voluntarily ceded time to one another. This approach, which

1064-633: A refinement of the previous OS X version, Leopard. Much of the software in Mac OS X was extensively rewritten for this release in order to take full advantage of modern Macintosh hardware and software technologies ( 64-bit , Cocoa , etc.). New programming frameworks, such as OpenCL , were created, allowing software developers to use graphics cards in their applications. It was also the first Mac OS release since System 7.1.1 to not support Macs using PowerPC processors, as Apple dropped support for them and focused on Intel-based products . As support for Rosetta

1140-512: A result, a computer executes segments of multiple tasks in an interleaved manner, while the tasks share common processing resources such as central processing units (CPUs) and main memory . Multitasking automatically interrupts the running program, saving its state (partial results, memory contents and computer register contents) and loading the saved state of another program and transferring control to it. This " context switch " may be initiated at fixed time intervals ( pre-emptive multitasking ), or

1216-478: A similar purpose to Nvidia 's C for CUDA and Microsoft 's Direct3D 11 compute shaders. It only works with the following Mac GPUs: NVIDIA GeForce 320M, GT 330M, 9400M, 9600M GT, 8600M GT, GT 120, GT 130, GTX 285, 8800 GT, 8800 GS, Quadro FX 4800, FX 5600 and ATI Radeon HD 4670, HD 4850, HD 4870, HD 5670, HD 5750, HD 5770, HD 5870, HD 6490M, HD 6750M, HD 6770M, HD 6970M. If the system does not possess one of these compatible GPUs, OpenCL code will instead execute on

1292-466: A single processor might be shared between calculations of machine movement, communications, and user interface. Often multitasking operating systems include measures to change the priority of individual tasks, so that important jobs receive more processor time than those considered less significant. Depending on the operating system, a task might be as large as an entire application program, or might be made up of smaller threads that carry out portions of

1368-528: A smaller volume would take up much less space than if they resided on a large partition. The same problem existed in the FAT16 file system. HFS saves the case of a file that is created or renamed but is case-insensitive in operation. Mac OS X 10.6 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

1444-631: A system with a few hundred kilobytes of storage and perhaps a hundred files, but as the systems grew into megabytes and thousands of files, the performance degraded rapidly. The solution was to replace MFS's directory structure with one more suitable to larger file systems. HFS replaced the flat table structure with the Catalog File which uses a B-tree structure that could be searched very quickly regardless of size. HFS also redesigned various structures to be able to hold larger numbers, 16-bit integers being replaced by 32-bit almost universally. Oddly, one of

1520-460: A time, meaning that many programs may be waiting in queue due to one program "hogging" the system. It is also a serious reliability concern, as damage to this file can destroy the entire file system. This contrasts with other file systems that store file and directory records in separate structures (such as DOS's FAT file system or the Unix File System ), where having structure distributed across

1596-500: A variant to threads, named fibers , that are scheduled cooperatively. On operating systems that do not provide fibers, an application may implement its own fibers using repeated calls to worker functions. Fibers are even more lightweight than threads, and somewhat easier to program with, although they tend to lose some or all of the benefits of threads on machines with multiple processors . Some systems directly support multithreading in hardware . Essential to any multitasking system

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1672-414: A welcome video at first boot after installation. Reception of Snow Leopard was positive; see the section below. Apple states the following basic Snow Leopard system requirements are: Additional requirements to use certain features: Snow Leopard drops support for PowerPC -based Macs (e.g., Power Macs , PowerBooks , iBooks , iMacs (G4 and G5), all eMacs , plus pre-February 2006 Mac Minis and

1748-495: Is 16 KB, so even a 1 byte file would take up 16 KB of disk space. This situation was less of a problem for users having large files (such as pictures, databases or audio) because these larger files wasted less space as a percentage of their file size. Users with many small files, on the other hand, could lose a copious amount of space due to large allocation block size. This made partitioning disks into smaller logical volumes very appealing for Mac users, because small documents stored on

1824-410: Is a common feature of computer operating systems since at least the 1960s. It allows more efficient use of the computer hardware; when a program is waiting for some external event such as a user input or an input/output transfer with a peripheral to complete, the central processor can still be used with another program. In a time-sharing system, multiple human operators use the same processor as if it

1900-453: Is a must-have (especially with Outlook for Mac on the way). With a ton of technological improvements, Snow Leopard is worth the $ 29 upgrade fee." On October 21, 2009, SFGate blogger Yobie Benjamin wrote that the "MacBook Pro that came preloaded with Snow Leopard kicks butt and is a screaming fast machine", but "when I tried to upgrade one of my 'older' MacBooks, it was a fricking disaster from hell". Apart from upgrading, Benjamin also tried

1976-453: Is a new blue and gray, as well as a solid kelp which serves as the "green wallpaper." The default "space nebula" wallpaper has been updated as well. Mac OS X Tiger added limited support for 64-bit applications on machines with 64-bit processors; Leopard extended the support for 64-bit applications to include applications using most of Mac OS X's libraries and frameworks. In Snow Leopard, most built-in applications have been rebuilt to use

2052-728: Is more vulnerable to attack than Microsoft Windows for lacking full address space layout randomization (ASLR) since Mac OS X Leopard, a technology that Microsoft started implementing in Windows Vista . The Safari web browser has received updates to version 6.0 in Lion and Mountain Lion, but not in Snow Leopard. Snow Leopard breaks compatibility with several older versions of some applications, such as Parallels Desktop 3.0, versions of Aperture before 2.1.1, and versions of Keynote before 2.0.2, among other software. Apple has also published

2128-402: Is no longer supported." However, read-only HFS Standard support continued to work until the release of macOS 10.15 , ending official support for classic HFS Standard after 35 years. A storage volume is inherently divided into logical blocks of 512 bytes. The Hierarchical File System groups these logical blocks into allocation blocks , which can contain one or more logical blocks, depending on

2204-400: Is still used today on RISC OS systems. As a cooperatively multitasked system relies on each process regularly giving up time to other processes on the system, one poorly designed program can consume all of the CPU time for itself, either by performing extensive calculations or by busy waiting ; both would cause the whole system to hang . In a server environment, this is a hazard that makes

2280-400: Is to safely and effectively share access to system resources. Access to memory must be strictly managed to ensure that no process can inadvertently or deliberately read or write to memory locations outside the process's address space. This is done for the purpose of general system stability and data integrity, as well as data security. In general, memory access management is a responsibility of

2356-659: The Classic Mac OS . In 2001 Apple switched to the NeXTSTEP -influenced Mac OS X . A similar model is used in Windows 9x and the Windows NT family , where native 32-bit applications are multitasked preemptively. 64-bit editions of Windows, both for the x86-64 and Itanium architectures, no longer support legacy 16-bit applications, and thus provide preemptive multitasking for all supported applications. Another reason for multitasking

Hierarchical File System (Apple) - Misplaced Pages Continue

2432-747: The Finder was completely rewritten in Cocoa , it did not receive a major user interface overhaul. Instead, the interface has been modified in several areas to promote ease of use. These changes include: As with most upgrades of Mac OS X, new wallpapers are available. There are new wallpapers in the Nature (two of which are of snow leopards ), Plants and Black and White sub-folders under the Apple folder. Furthermore, there are new Apple wallpaper sub-folders with multiple wallpapers: New solid colors can be used as wallpapers as well. There

2508-553: The H.264 decoder in QuickTime and browser plug-ins as a separate process in Safari . Secure virtual memory was an option in earlier releases on Snow Leopard, but the checkbox to disable it was removed later. An anti- malware feature was also added to the system that alerts the user if malware is detected. Mac OS X 10.6.8 added regular malware definition updates. Computer security researcher Charlie Miller claims that OS X Snow Leopard

2584-494: The Mac App Store introduced in the Snow Leopard 10.6.6 update. Snow Leopard is the last version of Mac OS X that supports the 32-bit Intel Core Solo and Intel Core Duo CPUs . Because of this, Snow Leopard still remained somewhat popular alongside OS X Lion, despite its lack of continued support, mostly because of its ability to run PowerPC-based applications. Snow Leopard is also the last release of Mac OS X to ship with

2660-642: The Power Mac G4 Cube ), although PowerPC applications are supported via Rosetta , which is now an optional install. In 2020, two developer previews of Snow Leopard that are universal appeared on the Internet that can be booted on select G4 and G5 Power Macs with modification and patching. Snow Leopard is available as an upgrade for Intel-based Macintosh computers. Single-user licenses and "family pack" licenses for up to five computers are available. For qualifying Mac computers bought after June 8, 2009, Apple offered

2736-474: The Sinclair QL followed in 1984, but it was not a big success. Commodore's Amiga was released the following year, offering a combination of multitasking and multimedia capabilities. Microsoft made preemptive multitasking a core feature of their flagship operating system in the early 1990s when developing Windows NT 3.1 and then Windows 95 . In 1988 Apple offered A/UX as a UNIX System V -based alternative to

2812-464: The sleep proxy service implemented in AirPort and Time Capsule routers, so that the computer can sleep while the router responds to mDNS queries. Should the request require the host computer to wake up , the router sends the necessary special wake-up-packet to the sleeping computer. Apple strengthened Mac OS X by implementing stack protection , and sandboxing more Mac OS X components such as

2888-412: The "Single Use" license: The Snow Leopard single user license will be available for a suggested retail price of $ 29 (US) (emphasis added) However, even if the retail edition of Snow Leopard is in fact a "Leopard Upgrade", the company has acknowledged that there is no technical barrier in that edition preventing a direct upgrade from Mac OS X "Tiger". The Leopard Upgrade license explicitly applies to

2964-447: The 64-bit x86-64 architecture (excluding iTunes , Front Row , Grapher and DVD Player applications). They will run in 32-bit mode on machines with 32-bit processors, and in 64-bit mode on machines with 64-bit processors. In addition, the Mac OS X kernel has been rebuilt to run in 64-bit mode on some machines. On those machines, Snow Leopard supports up to 16 terabytes of RAM. Newer Xserve and Mac Pro machines will run

3040-596: The Apple Software on a single Apple-branded computer at a time. It is not entirely clear which license is offered with the retail version of Snow Leopard. As noted above, Apple's website advertised this version as an "upgrade from Mac OS X Leopard for $ 29" and suggest that others upgrade using the Mac Box Set, implying the stand-alone retail version to be a "Leopard Upgrade" license. On the other hand, some Apple press materials appear to indicate that this version is, in fact,

3116-429: The CPU (" CPU bound "). In primitive systems, the software would often " poll ", or " busywait " while waiting for requested input (such as disk, keyboard or network input). During this time, the system was not performing useful work. With the advent of interrupts and preemptive multitasking, I/O bound processes could be "blocked", or put on hold, pending the arrival of the necessary data, allowing other processes to utilize

Hierarchical File System (Apple) - Misplaced Pages Continue

3192-555: The CPU. As the arrival of the requested data would generate an interrupt, blocked processes could be guaranteed a timely return to execution. Possibly the earliest preemptive multitasking OS available to home users was Microware 's OS-9 , available for computers based on the Motorola 6809 such as the TRS-80 Color Computer 2 , with the operating system supplied by Tandy as an upgrade for disk-equipped systems. Sinclair QDOS on

3268-527: The Macintosh in September 1985, where it was loaded into RAM from a MFS floppy disk on boot using a patch file ("Hard Disk 20"). However, HFS was not widely introduced until it was included in the 128K ROM that debuted with the Macintosh Plus in January 1986 along with the larger 800 KB floppy disk drive for the Macintosh that also used HFS. The introduction of HFS was the first advancement by Apple to leave

3344-461: The Up-To-Date Program (US$ 9.95) for Macs bought between June 8 and December 26, 2009 and the installation discs provided through this program are clearly marked as upgrades unlike either of the retail editions. Mac OS X Snow Leopard is a release that refined the existing feature set, expanded the technological capabilities of the operating system, and improved application efficiency. Many of

3420-405: The allocation block size. When disks were small, this was of little consequence, because the individual allocation block size was trivial, but as disks started to approach the 1 GB mark, the smallest amount of space that any file could occupy (a single allocation block) became excessively large, wasting significant amounts of disk space. For example, on a 1 GB disk, the allocation block size under HFS

3496-462: The changes involve how the system works in the background and are not intended to be seen by the user. For example, the Finder application was completely rewritten in the Cocoa application programming interface , from its previous Carbon codebase. Despite significant changes in the software, users will experience almost no changes in the user interface. Snow Leopard includes the following changes: While

3572-496: The context of this program was stored away, and the second program in memory was given a chance to run. The process continued until all programs finished running. The use of multiprogramming was enhanced by the arrival of virtual memory and virtual machine technology, which enabled individual programs to make use of memory and operating system resources as if other concurrently running programs were, for all practical purposes, nonexistent. Multiprogramming gives no guarantee that

3648-466: The disk means that damaging a single directory is generally non-fatal and the data may possibly be re-constructed with data held in the non-damaged portions. Additionally, the limit of 65,535 allocation blocks resulted in files having a "minimum" size equivalent 1/65,535th the size of the disk. Thus, any given volume, no matter its size, could only store a maximum of 65,535 files. Moreover, any file would be allocated more space than it actually needed, up to

3724-567: The early 2009 Mac Mini and MacBook may be capable of running the 64-bit kernel; however, Apple has set these models to boot into the 32-bit kernel. With some tweaking, the Unibody MacBook can be set to boot the 64-bit kernel. Grand Central Dispatch (GCD) uses the multiple processor cores now in every new Macintosh for more efficient performance. Due to the complexity of multithreaded programming and technical difficulties traditionally involved in making applications optimized for multicore CPUs,

3800-433: The early days of computing, CPU time was expensive, and peripherals were very slow. When the computer ran a program that needed access to a peripheral, the central processing unit (CPU) would have to stop executing program instructions while the peripheral processed the data. This was usually very inefficient. Multiprogramming is a computing technique that enables multiple programs to be concurrently loaded and executed into

3876-489: The entire environment unacceptably fragile. Preemptive multitasking allows the computer system to more reliably guarantee to each process a regular "slice" of operating time. It also allows the system to deal rapidly with important external events like incoming data, which might require the immediate attention of one or another process. Operating systems were developed to take advantage of these hardware capabilities and run multiple processes preemptively. Preemptive multitasking

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3952-415: The few places this "upsizing" did not take place was the file directory itself, which limits HFS to a total of 65,535 files on each logical disk. While HFS is a proprietary file system format, it is well-documented; there are usually solutions available to access HFS-formatted disks from most modern operating systems . Apple introduced HFS out of necessity with its first 20 MB hard disk offering for

4028-484: The idea that the most efficient way for cooperating processes to exchange data would be to share their entire memory space. Thus, threads are effectively processes that run in the same memory context and share other resources with their parent processes , such as open files. Threads are described as lightweight processes because switching between threads does not involve changing the memory context. While threads are scheduled preemptively, some operating systems provide

4104-463: 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 on new features. Apple famously marketed Snow Leopard as having "zero new features". Its name signified its goal to be

4180-484: The majority of computer applications do not effectively use multiple processor cores. As a result, additional processing power, compared to single-core machines, often goes unused. Grand Central Dispatch includes APIs to help programmers efficiently use these cores for parallel programming. Grand Central Dispatch abstracts the notion of threads away, and instead provides developers with the concept of queues—lists of jobs ( blocks of code ) that need to be executed. GCD takes

4256-482: The most part, everything that they experience on the Mac, from the 64-bit point of view, the applications, the operating system, is all going to be 64-bit, but that at this stage there were very few things, such as device drivers, that required 64-bit mode at the kernel level". With Mac OS X Snow Leopard only the following Apple computers run or are capable of running the 64-bit kernel: ^* Amit Singh has reported that

4332-468: The operating system kernel, in combination with hardware mechanisms that provide supporting functionalities, such as a memory management unit (MMU). If a process attempts to access a memory location outside its memory space, the MMU denies the request and signals the kernel to take appropriate actions; this usually results in forcibly terminating the offending process. Depending on the software and kernel design and

4408-453: The original file system which had been introduced over a year and a half earlier with the first Macintosh computer. HFS drew heavily upon Apple's first operating system with a hierarchical file system , SOS for the failed Apple III , which also served as the basis for hierarchical file systems on the Apple IIe and Apple Lisa . HFS was developed by Patrick Dirks and Bill Bruffey. It shared

4484-486: The overall program. A processor intended for use with multitasking operating systems may include special hardware to securely support multiple tasks, such as memory protection , and protection rings that ensure the supervisory software cannot be damaged or subverted by user-mode program errors. The term "multitasking" has become an international term, as the same word is used in many other languages such as German, Italian, Dutch, Romanian, Czech, Danish and Norwegian. In

4560-426: The power of graphics processing units (GPUs) to leverage them in any application, and not just for graphics-intensive applications like 3D games. OpenCL automatically optimizes for the kind of graphics processor in the Mac, adjusting itself to the available processing power. OpenCL provides consistent numeric precision and accuracy, fixing a problem that has hampered GPU-based programming in the past. OpenCL includes

4636-538: The price of Snow Leopard dropped from the $ 129 Apple charged for previous versions of Mac OS X to $ 29. Engadget's opinion was that this could be largely because most users would not see a noticeable change in the look and feel of the system. However, most reviews commented on the large improvement in speed of the native Mac OS X applications Finder , iCal , Mail , etc. CNET editors gave it 4 stars out of 5, stating "Intel Mac users will like Snow Leopard's smartly designed interface enhancements, and its Exchange support

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4712-571: The responsibility of distributing the jobs among actual threads and cores , and clearing up unused memory created by inactive or old threads to achieve maximum performance. Apple is also releasing APIs for Grand Central Dispatch for developers to use in their applications and also to analyze specific blocks of code running on Grand Central Dispatch. A new C and Objective-C language feature named " Blocks " facilitates creation of code that will easily optimize to take advantage of Grand Central Dispatch. OpenCL (Open Computing Language) addresses

4788-518: The running process hits a point where it has to wait for some portion of memory to be reloaded from secondary storage. Processes that are entirely independent are not much trouble to program in a multitasking environment. Most of the complexity in multitasking systems comes from the need to share computer resources between tasks and to synchronize the operation of co-operating tasks. Various concurrent computing techniques are used to avoid potential problems caused by multiple tasks attempting to access

4864-422: The running program may be coded to signal to the supervisory software when it can be interrupted ( cooperative multitasking ). Multitasking does not require parallel execution of multiple tasks at exactly the same time; instead, it allows more than one task to advance over a given period of time. Even on multiprocessor computers, multitasking allows many more tasks to be run than there are CPUs. Multitasking

4940-801: The specific error in question, the user may receive an access violation error message such as "segmentation fault". In a well designed and correctly implemented multitasking system, a given process can never directly access memory that belongs to another process. An exception to this rule is in the case of shared memory; for example, in the System V inter-process communication mechanism the kernel allocates memory to be mutually shared by multiple processes. Such features are often used by database management software such as PostgreSQL. Inadequate memory protection mechanisms, either due to flaws in their design or poor implementations, allow for security vulnerabilities that may be potentially exploited by malicious software. Use of

5016-566: The system's CPU. CUPS (the printing system used in many Unix-like operating systems) has been updated to version 1.4 which provides improved driver, networking, and Kerberos support along with performance improvements. CUPS 1.4 is also the first implementation of the Internet Printing Protocol version 2.1. Power management has been improved, with implementation of a new wake on demand feature supported on more recent Macintosh hardware. Wake on demand takes advantage of

5092-428: The terms and conditions of this License, you are granted a limited non-exclusive license to install, use and run one (1) copy of the Apple Software on a single Apple-branded computer as long as that computer has a properly licensed copy of Mac OS X Leopard already installed on it. Subject to the terms and conditions of this License ... you are granted a limited non-exclusive license to install, use and run one (1) copy of

5168-400: The total size of the volume. HFS uses a 16-bit value to address allocation blocks, limiting the number of allocation blocks to 65,535 (2-1). Five structures make up an HFS volume: The Catalog File, which stores all the file and directory records in a single data structure, results in performance problems when the system allows multitasking , as only one program can write to this structure at

5244-514: The week. Testmac.com highlighted other unexpected improvements including the release of a new version of Boot Camp , version 3.0, a cleaner, popup software update process and screen and video recording in the new QuickTime Player . Computer multitasking In computing , multitasking is the concurrent execution of multiple tasks (also known as processes ) over a certain period of time. New tasks can interrupt already started ones before they finish, instead of waiting for them to end. As

5320-405: Was dedicated to their use, while behind the scenes the computer is serving many users by multitasking their individual programs. In multiprogramming systems, a task runs until it must wait for an external event or until the operating system's scheduler forcibly swaps the running task out of the CPU. Real-time systems such as those designed to control industrial robots, require timely processing;

5396-576: Was dropped in Mac OS X Lion , Snow Leopard is the last version of Mac OS X that is able to run PowerPC-only applications. Snow Leopard was succeeded by OS X Lion (version 10.7) on July 20, 2011. For several years, Apple continued to sell Snow Leopard at its online store for the benefit of users that required Snow Leopard in order to upgrade to later versions of OS X. Snow Leopard was the last version of Mac OS X to be distributed primarily through optical disc , as all further releases were mainly distributed through

5472-469: Was eventually supported by many computer operating systems , is known today as cooperative multitasking. Although it is now rarely used in larger systems except for specific applications such as CICS or the JES2 subsystem, cooperative multitasking was once the only scheduling scheme employed by Microsoft Windows and classic Mac OS to enable multiple applications to run simultaneously. Cooperative multitasking

5548-680: Was implemented in the PDP-6 Monitor and Multics in 1964, in OS/360 MFT in 1967, and in Unix in 1969, and was available in some operating systems for computers as small as DEC's PDP-8; it is a core feature of all Unix-like operating systems, such as Linux , Solaris and BSD with its derivatives , as well as modern versions of Windows. At any specific time, processes can be grouped into two categories: those that are waiting for input or output (called " I/O bound "), and those that are fully utilizing

5624-725: Was in the design of real-time computing systems, where there are a number of possibly unrelated external activities needed to be controlled by a single processor system. In such systems a hierarchical interrupt system is coupled with process prioritization to ensure that key activities were given a greater share of available process time . As multitasking greatly improved the throughput of computers, programmers started to implement applications as sets of cooperating processes (e. g., one process gathering input data, one process processing input data, one process writing out results on disk). This, however, required some tools to allow processes to efficiently exchange data. Threads were born from

5700-413: Was introduced to overcome some of the performance problems that arrived with the introduction of larger media, notably hard drives . The main concern was the time needed to display the contents of a folder. Under MFS all of the file and directory listing information was stored in a single file, which the system had to search to build a list of the files stored in a particular folder. This worked well with

5776-463: Was publicly unveiled on June 9, 2008 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 the low price, initial sales of Snow Leopard were significantly higher than that of its predecessors whose price started at $ 129 USD. The release of Snow Leopard came nearly two years after

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