The Disk II Floppy Disk Subsystem rendered as Disk ][, is a 5 1⁄4-inch floppy disk drive designed by Steve Wozniak and manufactured by Apple Computer, Inc. It went on sale in June 1978 at a retail price of US$495 for pre-order; the Disk II was designed for use with the Apple II personal computer family to replace the slower cassette tape storage. These floppy drives cannot be used with any Macintosh without an Apple IIe Card as doing so will damage the drive or the controller. Apple produced at least six variants of the basic 5 1⁄4-inch Disk II concept over the course of the Apple II series' lifetime: The Disk II, the Disk III, the DuoDisk, the Disk IIc, the UniDisk 5.25" and the Apple 5.25 Drive. While all of these drives look different and they use four different connector types, they're all electronically similar, can all use the same low-level disk format, are all interchangeable with the use of simple adapters, consisting of no more than two plugs and some wires between them. Most DuoDisk drives, the Disk IIc, the UniDisk 5.25" and the AppleDisk 5.25" use the same 19-pin D-Sub connector, so they are directly interchangeable.
The only 5 1⁄4" drive Apple sold aside from the Disk II family was a 360k MFM unit made to allow Mac IIs and SEs to read PC floppy disks. This is not the case with Apple's 3 1⁄2-inch drives, which use several different disk formats and several different interfaces, electronically quite dissimilar in models using the same connector. Apple did not offer a disk drive for the Apple II, which used data cassette storage like other microcomputers of the time. Apple founder and executive Mike Markkula asked cofounder Steve Wozniak to design a drive system for the computer after finding that a checkbook-balancing program Markkula had written took too long to load from tape. Wozniak knew nothing about disk controllers, but while at Hewlett-Packard had designed a simple, five-chip circuit to operate a Shugart Associates drive. Wozniak studied others' more complex floppy controllers, he believed that his simpler design lacked their features, but realized that they were less sophisticated. Following the Shugart controller's manual, Wozniak attempted to develop an FM-type controller with 10 sector per track storage, but realized that Group Coded Recording could fit 13 sectors per track.
Wozniak called the resultant Disk II system "my most incredible experience at Apple and the finest job I did", credited it and VisiCalc with the Apple II's success. The Disk II was successful for Apple, being the cheapest floppy disk system sold up to that point and immensely profitable for the company, in addition to having nearly 20% more storage space than standard FM drives. For a while, the only direct competitor in the microcomputer industry was the TRS-80 Model I, which had used only standard FM storage for 85k. Both the Atari 8-bit and Commodore 64's disk drives' throughputs were much slower than the Disk II's 15K bytes per second affecting their ability to compete in the business market. However, the advantage of Wozniak's design was somewhat nullified when the cost of double-density MFM controllers dropped only a year after the Disk II's introduction; the Apple II's lack of a disk drive was "a glaring weakness" in what was otherwise intended to be a polished, professional product.
Speaking Osborne 1 designer Lee Felsenstein stated, "The difference between cassette and disk systems was the difference between hobbyist devices and a computer. You couldn't have expected, VisiCalc, to run on a cassette system." Recognizing that the II needed a disk drive to be taken Apple set out to develop a disk drive and a DOS to run it. Wozniak spent the 1977 Christmas holidays adapting his controller design, which reduced the number of chips used by a factor of 10 compared to existing controllers. Still lacking a DOS, with Wozniak inexperienced in operating system design, Steve Jobs approached Shepardson Microsystems with the project. On April 10, 1978 Apple signed a contract for $13,000 with Shepardson to develop the DOS; the initial Disk II drives were modifications of the Shugart SA-400, the first commercially available 5 1⁄4" diskette drive. Apple purchased only the bare drive mechanisms without the standard SA-400 controller board, replaced it with Wozniak's board design, stamped the Apple rainbow logo onto the faceplate.
Early production at Apple was handled by two people, they assembled 30 drives a day. By 1982, Apple switched to Alps drives for cost reasons. Shortly after the disk drive project began in late 1977, Steve Jobs made several trips to Shugart's offices announcing that he wanted a disk drive that would cost just $100. After Wozniak finished studying IBM disk controller designs, Jobs demanded that Shugart sell them a stripped disk drive that had no controller board, index sensor, load solenoids, or track zero sensor. Although puzzled by this request, Shugart complied and provided Apple with 25 drive mechanisms that they could use as prototypes in developing a disk system for the Apple II; the prototypes received the designation of SA-390. Steve Wozniak found out that some of the SA-390 drives didn't work without adjustments while others wouldn't work at all. Fellow engineer Cliff Huston came up with several procedures for resuscitating the faulty drives on the assembly line; when Apple sent an order into Shugart for more SA-390s, a Shugart engineer admitted that the disk drive manufacturer had been scamming Apple and that the SA-390s were rejected SA-400s that had failed to pass
The Apple IIe is the third model in the Apple II series of personal computers produced by Apple Computer. The e in the name stands for enhanced, referring to the fact that several popular features were now built-in that were only available as upgrades or add-ons in earlier models. Improved expandability combined with the new features made for a attractive general-purpose machine to first-time computer shoppers; as the last surviving model of the Apple II computer line before discontinuation, having been manufactured and sold for nearly 11 years with few changes, the IIe earned the distinction of being the longest-lived computer in Apple's history. Apple Computer planned to discontinue the Apple II series after the introduction of the Apple III in 1980. Management believed that "once the Apple III was out, the Apple II would stop selling in six months", cofounder Steve Wozniak said. By the time IBM released the rival IBM PC in 1981, the Apple II's technology was four years old. In September 1981 InfoWorld reported—below the PC's announcement—that Apple was secretly developing three new computers "to be ready for release within a year": Lisa, "McIntosh", "Diana".
Describing the last as a software-compatible Apple II replacement—"A 6502 machine using custom LSI" and a simpler motherboard—it said that Diana "was ready for release months ago" but decided to improve the design to better compete with the Xerox 820. "Now it appears that when Diana is ready for release, it will offer features and a price that will make the Apple II uncompetitive", the magazine wrote."Apple's plans to phase out the Apple II have been delayed by complications in the design of the Apple III", the article said. After the Apple III struggled, management decided in 1981 that the further continuation of the Apple II was in the company's best interest. After 3 1⁄2 years of the Apple II Plus at a standstill, came the introduction of a new Apple II model — the Apple IIe; the Apple IIe was released in the successor to the Apple II Plus. The Apple IIe was the first Apple computer with a custom ASIC chip, which reduced much of the old discrete IC-based circuitry to a single chip; this change resulted in reducing the size of the motherboard.
Some of the hardware features of the Apple III were borrowed in the design of the Apple IIe, some from incorporating the Apple II Plus Language card. The culmination of these changes led to increased sales and greater market share of home and small business use. One of the most notable improvements of the Apple IIe is the addition of a full ASCII character set and keyboard; the most important addition is the ability to display lower-case letters. Other keyboard improvements include four-way cursor control and standard editing keys, two special Apple modifier keys, a safe off-to-side relocation of the "Reset" key; the auto-repeat function is now automatic, no longer requiring the "REPT" key found on the keyboards of previous models. The machine came standard with 64 KB RAM, with the equivalent of a built-in Apple Language Card in its circuitry, had a new special "Auxiliary slot" for adding more memory via bank-switching RAM cards. Through this slot it includes built-in support for an 80-column text display on monitors and could be doubled to 128 KB RAM by alternatively plugging in Apple's Extended 80-Column Text Card.
As time progressed more memory could be added through third-party cards using the same bank-switching slot or, general-purpose slot cards that addressed memory 1 byte at a time. A new ROM diagnostic routine could be invoked to test the motherboard for faults and test its main bank of memory; the Apple IIe lowered production costs and improved reliability by merging the function of several off-the-shelf ICs into single custom chips, reducing total chip count to 31. The IIe switched to using newer single-voltage 4164 DRAM chips instead of the unreliable triple-voltage 4116 DRAM in the II/II+. For this reason the motherboard design is much cleaner and runs cooler as well, with enough room to add a pin-connector for an external numeric keypad. Added was a backport-accessible DE-9 joystick connector, making it far easier for users to add and remove game and input devices. Improved were port openings for expansion cards. Rather than cutout V-shaped slot openings as in the Apple II and II Plus, the IIe has a variety of different-sized openings, with thumb-screw holes, to accommodate mounting interface cards with DB-xx and DE-xx connectors.
Although the lower IC count improved reliability over previous Apple II models, Apple still retained the practice of socketing all ICs so that servicing and replacement could be performed more easily. Later-production IIe models had the RAM soldered to the system board rather than socketed. Despite the hardware changes, the IIe maintains a high degree of backwards compatibility with the previous models, allowing most hardwa
A patch is a set of changes to a computer program or its supporting data designed to update, fix, or improve it. This includes fixing security vulnerabilities and other bugs, with such patches being called bugfixes or bug fixes, improving the usability or performance. Although meant to fix problems, poorly designed patches can sometimes introduce new problems. In some special cases updates may knowingly break the functionality or disable a device, for instance, by removing components for which the update provider is no longer licensed. Patch management is a part of lifecycle management, is the process of using a strategy and plan of what patches should be applied to which systems at a specified time. Patches for proprietary software are distributed as executable files instead of source code; this type of patch modifies the program executable—the program the user runs—either by modifying the binary file to include the fixes or by replacing it. On early 8-bit microcomputers, for example the Radio Shack TRS-80, the operating system included a PATCH utility which accepted patch data from a text file and applied the fixes to the target program's executable binary file.
Small in-memory patches could be manually applied with the system debug utility, such as CP/M's DDT or MS-DOS's DEBUG debuggers. Programmers working in interpreted BASIC used the POKE command to temporarily alter the functionality of a system service routine. Patches can circulate in the form of source code modifications. In this case, the patches consist of textual differences between two source code files, called "diffs"; these types of patches come out of open-source software projects. In these cases, developers expect users to compile the changed files themselves; because the word "patch" carries the connotation of a small fix, large fixes may use different nomenclature. Bulky patches or patches that change a program may circulate as "service packs" or as "software updates". Microsoft Windows NT and its successors use the "service pack" terminology. IBM used the terms "FixPaks" and "Corrective Service Diskette" to refer to these updates. Software suppliers distributed patches on paper tape or on punched cards, expecting the recipient to cut out the indicated part of the original tape, patch in the replacement segment.
Patch distributions used magnetic tape. After the invention of removable disk drives, patches came from the software developer via a disk or CD-ROM via mail. With the available Internet access, downloading patches from the developer's web site or through automated software updates became available to the end-users. Starting with Apple's Mac OS 9 and Microsoft's Windows ME, PC operating systems gained the ability to get automatic software updates via the Internet. Computer programs can coordinate patches to update a target program. Automation simplifies the end-user's task – they need only to execute an update program, whereupon that program makes sure that updating the target takes place and correctly. Service packs for Microsoft Windows NT and its successors and for many commercial software products adopt such automated strategies; some programs can update themselves via the Internet with little or no intervention on the part of users. The maintenance of server software and of operating systems takes place in this manner.
In situations where system administrators control a number of computers, this sort of automation helps to maintain consistency. The application of security patches occurs in this manner; the size of patches may vary from a few bytes to hundreds of megabytes. In particular, patches can become quite large when the changes add or replace non-program data, such as graphics and sounds files; such situations occur in the patching of computer games. Compared with the initial installation of software, patches do not take long to apply. In the case of operating systems and computer server software, patches have the important role of fixing security holes; some critical patches involve issues with drivers. Patches may require prior application of other patches, or may require prior or concurrent updates of several independent software components. To facilitate updates, operating systems provide automatic or semi-automatic updating facilities. Automatic updates have not succeeded in gaining widespread popularity in corporate computing environments because of the aforementioned glitches, but because administrators fear that software companies may gain unlimited control over their computers.
Package management systems can offer various degrees of patch automation. Usage of automatic updates has become far more widespread in the consumer market, due to the fact that Microsoft Windows added support for them, Service Pack 2 of Windows XP enabled them by default. Cautious users system administrators, tend to put off applying patches until they can verify the stability of the fixes. Microsoft SUS supports this. In the cases of large patches or of significant changes, distributors limit availability of patches to qualified developers as a beta test. Applying patches to firmware poses special challenges, as it involves the provisioning of new firmware images, rather than applying only the differences from the previous version; the patch consists of a firmware image in form of binary d
Apple II Plus
The Apple II Plus is the second model of the Apple II series of personal computers produced by Apple Computer, Inc. It was sold from June 1979 to December 1982. 380,000 II Pluses were sold during its four years in production before being replaced by the IIe in 1983. The Apple II Plus shipped with 16 KB, 32 KB or 48 KB of main RAM, expandable to 64 KB by means of the Language Card, an expansion card that could be installed in the computer's slot 0; the Apple's 6502 microprocessor could support a maximum of 64 KB of address space, a machine with 48KB RAM reached this limit because of the additional 12 KB of read-only memory and 4 KB of I/O addresses. For this reason, the extra RAM in the language card was bank-switched over the machine's built-in ROM, allowing code loaded into the additional memory to be used as if it were ROM. Users could thus load Integer BASIC into the language card from disk and switch between the Integer and Applesoft dialects of BASIC with DOS 3.3's INT and FP commands just as if they had the BASIC ROM expansion card.
The Language Card was required to use LOGO, Apple Pascal, FORTRAN 77. Apple Pascal and FORTRAN ran under a non-DOS operating system based on UCSD P-System, which had its own disk format and included a "virtual machine" that allowed it to run on many different types of hardware. First-year Apple II Pluses retained the original Apple II's jumper blocks to select the RAM size, but a drop in memory prices during 1980 resulted in all machines being shipped with 48k and the jumper blocks being removed. Shortly after the introduction of the II Plus in 1979, Microsoft came out with the Z-80 SoftCard, an expansion card for the Apple II line that allowed the use of CP/M and contained its own Z80 CPU and logic to adapt the Z80 CPU to the Apple bus; the SoftCard was popular and Microsoft's single most successful product for two years, although on the downside, it was limited to using the Apple II's GCR disk format and thus CP/M software either had to be obtained on Apple format disks or transferred via serial link from a different machine running CP/M.
The SoftCard shipped with CP/M 2.2 and a special version of MBASIC that supported a subset of Applesoft BASIC's graphics commands. Other third party CP/M cards for the Apple II offered additional memory, CP/M 3.0, CPU speeds up to 8Mhz. The II Plus had the so-called "Autostart ROMs", meaning that it will attempt to boot from disk on power-up. If no system disk is present, Drive 0 will spin endlessly until the user presses Ctrl+Reset to enter Applesoft BASIC. If DOS has not been booted up, the user will only be able to load and save files to cassette from BASIC; the II Plus had a revised version of BASIC known as Applesoft II which incorporated most of the functionality from Integer BASIC, including HGR graphics commands. Most II Pluses came with a "language card"; this was different from the language card sold for the original II, which contained Applesoft BASIC in ROM. Since the II Plus had Applesoft present in the ROMs on the system board, its language card contained RAM rather than ROM and if installed will boost the system to 64k.
While on the original II, Integer BASIC resided in ROM at $E000, this area contains RAM on the II Plus if a language card is present. Integer BASIC is not in ROM on the II Plus and is instead loaded by DOS 3.x during boot up into the RAM at $D000. The RAM containing Integer BASIC is banked out and the Applesoft ROM is present at $D000. If the user types "INT", Integer BASIC is activated by swapping out the Applesoft ROM and switching in the RAM with Integer BASIC. By typing "FP", Integer BASIC is switched out and Applesoft switched back in; the machine language monitor at $F800 may be banked out for RAM. Like the Apple II, the Apple II Plus has no lowercase functionality. All letters from the keyboard are upper-case, there is no caps lock key, there are no lowercase letters in the text-mode font stored in the computer's ROM. To display lowercase letters, some applications run in the slower hi-res graphics mode and use a custom font, rather than running in the fast text mode using the font in ROM.
Other programs those where both capitalization and text movement were important, such as word processors, use inverse text mode to represent text that would be uppercase when printed. Alternatively, users can install a custom ROM chip that contained lowercase letters in the font, or purchase one of several third-party 80-column cards that enable a text mode that can display 80-column, upper- and lower-case text; the Videx Videoterm and its many clones were popular. For lowercase input, since it is not possible to detect whether the keyboard's Shift keys are in use, the common "shift-key mod" connects the Shift key to one of the pins on the motherboard's paddle connector. Compatible applications, including nearly all word processors, can detect whether the shift key was being pressed; this modification involves adding wires inside the Apple II. Most applications that support lower-case letters can use the ESC key as a substitute lowercase toggle if the modification is not installed; the Apple II Plus, like its predecessor the Apple II, features a repeat key on its keyboard.
The key is located just to the left of the "RETURN" key. The II Plus is the last Apple Computer to have this key, as Apple computers would incorporate the ability to hold down a key for a period of time to repeat the key; the II Plus has a plastic case with a brass mesh running along
An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may include accounting software for cost allocation of processor time, mass storage and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is executed directly by the hardware and makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer – from cellular phones and video game consoles to web servers and supercomputers; the dominant desktop operating system is Microsoft Windows with a market share of around 82.74%. MacOS by Apple Inc. is in second place, the varieties of Linux are collectively in third place. In the mobile sector, use in 2017 is up to 70% of Google's Android and according to third quarter 2016 data, Android on smartphones is dominant with 87.5 percent and a growth rate 10.3 percent per year, followed by Apple's iOS with 12.1 percent and a per year decrease in market share of 5.2 percent, while other operating systems amount to just 0.3 percent.
Linux distributions are dominant in supercomputing sectors. Other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can only run one program at a time, while a multi-tasking operating system allows more than one program to be running in concurrency; this is achieved by time-sharing, where the available processor time is divided between multiple processes. These processes are each interrupted in time slices by a task-scheduling subsystem of the operating system. Multi-tasking may be characterized in co-operative types. In preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, such as Solaris and Linux—as well as non-Unix-like, such as AmigaOS—support preemptive multitasking. Cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking.
32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem. A multi-user operating system extends the basic concept of multi-tasking with facilities that identify processes and resources, such as disk space, belonging to multiple users, the system permits multiple users to interact with the system at the same time. Time-sharing operating systems schedule tasks for efficient use of the system and may include accounting software for cost allocation of processor time, mass storage and other resources to multiple users. A distributed operating system manages a group of distinct computers and makes them appear to be a single computer; the development of networked computers that could be linked and communicate with each other gave rise to distributed computing. Distributed computations are carried out on more than one machine; when computers in a group work in cooperation, they form a distributed system.
In an OS, distributed and cloud computing context, templating refers to creating a single virtual machine image as a guest operating system saving it as a tool for multiple running virtual machines. The technique is used both in virtualization and cloud computing management, is common in large server warehouses. Embedded operating systems are designed to be used in embedded computer systems, they are designed to operate on small machines like PDAs with less autonomy. They are able to operate with a limited number of resources, they are compact and efficient by design. Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is an operating system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, it uses specialized scheduling algorithms so that a deterministic nature of behavior is achieved. An event-driven system switches between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock interrupts.
A library operating system is one in which the services that a typical operating system provides, such as networking, are provided in the form of libraries and composed with the application and configuration code to construct a unikernel: a specialized, single address space, machine image that can be deployed to cloud or embedded environments. Early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could automatically run different programs in succession to speed up processing. Operating systems did not exist in their more complex forms until the early 1960s. Hardware features were added, that enabled use of runtime libraries and parallel processing; when personal computers became popular in the 1980s, operating systems were made for them similar in concept to those used on larger computers. In the 1940s, the earliest electronic digital systems had no operating systems.
Electronic systems of this time were programmed on rows of mechanical switches or by jumper wires on plug boards. These were special-purpose systems that, for example, generated ballistics tables for the military or controlled the pri
Apple Inc. is an American multinational technology company headquartered in Cupertino, that designs and sells consumer electronics, computer software, online services. It is considered one of the Big Four of technology along with Amazon and Facebook; the company's hardware products include the iPhone smartphone, the iPad tablet computer, the Mac personal computer, the iPod portable media player, the Apple Watch smartwatch, the Apple TV digital media player, the HomePod smart speaker. Apple's software includes the macOS and iOS operating systems, the iTunes media player, the Safari web browser, the iLife and iWork creativity and productivity suites, as well as professional applications like Final Cut Pro, Logic Pro, Xcode, its online services include the iTunes Store, the iOS App Store, Mac App Store, Apple Music, Apple TV+, iMessage, iCloud. Other services include Apple Store, Genius Bar, AppleCare, Apple Pay, Apple Pay Cash, Apple Card. Apple was founded by Steve Jobs, Steve Wozniak, Ronald Wayne in April 1976 to develop and sell Wozniak's Apple I personal computer, though Wayne sold his share back within 12 days.
It was incorporated as Apple Computer, Inc. in January 1977, sales of its computers, including the Apple II, grew quickly. Within a few years and Wozniak had hired a staff of computer designers and had a production line. Apple went public in 1980 to instant financial success. Over the next few years, Apple shipped new computers featuring innovative graphical user interfaces, such as the original Macintosh in 1984, Apple's marketing advertisements for its products received widespread critical acclaim. However, the high price of its products and limited application library caused problems, as did power struggles between executives. In 1985, Wozniak departed Apple amicably and remained an honorary employee, while Jobs and others resigned to found NeXT; as the market for personal computers expanded and evolved through the 1990s, Apple lost market share to the lower-priced duopoly of Microsoft Windows on Intel PC clones. The board recruited CEO Gil Amelio to what would be a 500-day charge for him to rehabilitate the financially troubled company—reshaping it with layoffs, executive restructuring, product focus.
In 1997, he led Apple to buy NeXT, solving the failed operating system strategy and bringing Jobs back. Jobs pensively regained leadership status, becoming CEO in 2000. Apple swiftly returned to profitability under the revitalizing Think different campaign, as he rebuilt Apple's status by launching the iMac in 1998, opening the retail chain of Apple Stores in 2001, acquiring numerous companies to broaden the software portfolio. In January 2007, Jobs renamed the company Apple Inc. reflecting its shifted focus toward consumer electronics, launched the iPhone to great critical acclaim and financial success. In August 2011, Jobs resigned as CEO due to health complications, Tim Cook became the new CEO. Two months Jobs died, marking the end of an era for the company. Apple is well known for its size and revenues, its worldwide annual revenue totaled $265 billion for the 2018 fiscal year. Apple is the world's largest information technology company by revenue and the world's third-largest mobile phone manufacturer after Samsung and Huawei.
In August 2018, Apple became the first public U. S. company to be valued at over $1 trillion. The company employs 123,000 full-time employees and maintains 504 retail stores in 24 countries as of 2018, it operates the iTunes Store, the world's largest music retailer. As of January 2018, more than 1.3 billion Apple products are in use worldwide. The company has a high level of brand loyalty and is ranked as the world's most valuable brand. However, Apple receives significant criticism regarding the labor practices of its contractors, its environmental practices and unethical business practices, including anti-competitive behavior, as well as the origins of source materials. Apple Computer Company was founded on April 1, 1976, by Steve Jobs, Steve Wozniak, Ronald Wayne; the company's first product is the Apple I, a computer designed and hand-built by Wozniak, first shown to the public at the Homebrew Computer Club. Apple I was sold as a motherboard —a base kit concept which would now not be marketed as a complete personal computer.
The Apple I went on sale in July 1976 and was market-priced at $666.66. Apple Computer, Inc. was incorporated on January 3, 1977, without Wayne, who had left and sold his share of the company back to Jobs and Wozniak for $800 only twelve days after having co-founded Apple. Multimillionaire Mike Markkula provided essential business expertise and funding of $250,000 during the incorporation of Apple. During the first five years of operations revenues grew exponentially, doubling about every four months. Between September 1977 and September 1980, yearly sales grew from $775,000 to $118 million, an average annual growth rate of 533%; the Apple II invented by Wozniak, was introduced on April 16, 1977, at the first West Coast Computer Faire. It differs from its major rivals, the TRS-80 and Commodore PET, because of its character cell-based color graphics and open architecture. While early Apple II models use ordinary cassette tapes as storage devices, they were superseded by the introduction of a 5 1⁄4-inch floppy disk drive and interface called the Disk II.
The Apple II was chosen to be the desktop platform for the first "killer app" of the business world: VisiCalc, a spreadsheet program. VisiCalc created a business market for the Apple II and gave home users an additional reason to buy an Apple II: compatibility with the office. Before VisiCalc, Apple had been a distant third place c
The Western Design Center 65C02 microprocessor is an enhanced CMOS version of the popular NMOS-based 8-bit MOS Technology 6502 microprocessor—the CMOS redesign being made by Bill Mensch in 1978. Over various periods of time, the 65C02 has been second-sourced by NCR, GTE, Rockwell and Sanyo; the 65C02 has been used in some home computers, as well as in embedded applications, including medical-grade implanted devices. The 65C02 is a low cost, general-purpose 8-bit microprocessor with a 16-bit program counter and address bus; the variable length instruction set and manually optimized core size are intended to make the 65C02 well suited for low power system-on-chip designs. A Verilog hardware description model is available for designing the W65C02S core into an application-specific integrated circuit or a field-programmable gate array; as is common in the semiconductor industry, WDC offers a development system, which includes a developer board, an in-circuit emulator and a software development system.
The W65C02S–14 is the production version of the 65C02 microprocessor, is available in PDIP, PLCC and QFP packages through distribution. The maximum supported ϕ2 clock speed is 14 MHz, indicated by the –14 part number suffix; the "S" designation indicates that the part has a static core, a feature that allows ϕ2 to be slowed down or stopped in either the high or low state with no loss of data. Typical microprocessors not implemented in CMOS have dynamic cores and will lose their internal register contents if they are not continuously clocked at a rate between some minimum and maximum specified values. 8-bit data bus 16-bit address bus 8-bit arithmetic logic unit 8-bit processor registers: accumulator stack pointer index registers status register 16-bit program counter 69 instructions, implemented by 212 operation codes 16 addressing modes, including zero page addressing Vector pull output indicates when interrupt vectors are being addressed Memory lock output indicates to other bus masters when a read-modify-write instruction is being processed WAit-for-Interrupt and SToP instructions reduce power consumption, decrease interrupt latency and enable synchronization with external events Supply voltage specified at 1.71 V to 5.25 V Current consumption of 0.15 and 1.5 mA per MHz at 1.89 V and 5.25 V Variable length instruction set, enabling code size optimization over fixed length instruction set processors, results in power savings Fully static circuitry allows stopping the clock to conserve power The W65C02S may be operated at any convenient supply voltage between 1.8 and 5 volts.
The data sheet AC characteristics table lists operational characteristics at 5 V at 14 MHz, 3.3 V or 3 V at 8 MHz, 2.5 V at 4 MHz, 1.8 V at 2 MHz. This information may be an artifact of an earlier data sheet, as a graph indicates that typical devices are capable of operation at higher speeds than suggested by the AC characteristics table, that reliable operation at 20 MHz should be attainable with VDD at 5 volts, assuming the supporting hardware will allow it; the W65C02S may be operated at non-integral clock rates such as 13.5 MHz, 14.31818 MHz, 14.75 MHz, 14.7456, etc. as long as VDD is sufficient to support the frequency. Designer Bill Mensch has pointed out that FMAX is affected by off-chip factors, such as the capacitive load on the microprocessor's pins. Minimizing load by using short signal tracks and fewest devices helps raise FMAX; the PLCC and QFP packages have less pin-to-pin capacitance than the PDIP package, are more economical in the use of printed circuit board space. WDC has reported that FPGA realizations of the W65C02S have been operated at 200 MHz.
The 65C02 shares its predecessor's 8-bit instruction set architecture and 16-bit memory address space $0000 to $FFFF allowing access to a total memory map of 64K. "Zero Page" spans $0000 to $00FF. "Page 1" is dedicated for the stack. On this processor the stack grows downwards with the stack pointer starting at $01FF and decrementing as the stack grows; the 65C02 adds a number of improvements and documented opcodes, the most useful being instructions that can push or pull the X and Y index registers to/from the stack. Undefined opcodes have been converted although of varying instruction lengths; the defective "indirect jump page wrap" instruction has been fixed, eliminating a source of trouble for unwary assembly language programmers. This instruction has been enhanced with. X register indexing, making it possible to code JMP, enabling the development of a simple jump table management methodology; some variants of the 65C02 feature individual bit manipulation operations. The 65SC02 was available, which lacked these operations.
Other problems with the 6502, fixed in the 65C02, relate to its program status register, which contains eight system flags. Some flags are reset under program control. Others reflect the status of the machine after bit manipulation instructions. 6502 status flags, with meanings when set: In all NMOS logic forms of the 6502, the decimal flag is not initialized to a known state following reset or when an interrupt is processed, which may lead to arbitrary behavior. This forces 6502 programmers to use the CLD ins