The Apple II Plus (stylized as Apple ][+) 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.[1] Approximately 380,000 II Pluses were sold during its four years in production before being replaced by the IIe in 1983.
Features[edit]
Aug 18, 2016 Apple II + Arduino + SD Card + SdFat = A2SdFat! August 18, 2016 dave. The Apple disk image utility. Iâve worked on a similar project with Rodney Ross to bring the Apple II Piâs virtual disk interface to the Super Serial Card using an Atmel processor and the SdFat library.
Memory[edit]
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, and 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 actually 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 also required to use LOGO, Apple Pascal, and 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.
CP/M[edit]
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 extremely 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, and CPU speeds up to 8Mhz.
Onboard Applesoft BASIC[edit]
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 completely different from the language card sold for the original II, which contained Applesoft BASIC in ROM. Since the II Plus already 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 (if a language card is present, otherwise this step is skipped--II Pluses without a language card cannot run Integer BASIC). Normally, 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 also be banked out for RAM.
Substitute lowercase functionality[edit]
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, and 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, primarily 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 especially 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 then detect whether the shift key was being pressed. This modification involves adding wires inside the Apple II; Apple distributed literature on how to build it, however, assuring readers that it was 'the most simple and least expensive addition anyone could do'.[2] Most applications that support lower-case letters can also use the ESC key as a substitute lowercase toggle if the modification is not installed.
Repeat key[edit]
The Apple II Plus, like its predecessor the Apple II, features a repeat key on its keyboard. The key is labeled 'REPT' and is located just to the left of the 'RETURN' key.[3][4] The II Plus is the last Apple Computer to have this key, as later Apple computers would incorporate the ability to hold down a key for a period of time to repeat the key.
Electromagnetic shielding[edit]
The II Plus has a plastic case with a brass mesh running along the inside of the case. This mesh helped reduce the electromagnetic interference emitted from the computer, keeping the machine in compliance with newly implemented FCC regulations covering microcomputers. Small grids of plastic pins, and sometimes Velcro® Brand Fasteners, were used to hold the case's top onto the computer. In comparison, the original Apple II lacked RF shielding and was often unusable with certain TVs and monitors (Apple recommended Sony TVs as they had better RF insulation than other brands).
Variants[edit]Apple II Europlus and J-Plus[edit]
After the success of the first Apple II in the United States, Apple expanded its market to include Europe and the Far East in 1978, with the Apple II Europlus (Europe) and the Apple II J-Plus (Japan). In these models, Apple made the necessary hardware, software and firmware changes in order to comply with standards outside of the US. The power supply was modified to accept the local voltage, and in the European model the video output signal was changed from color NTSC to monochrome PAL by changing some jumpers on the motherboard and using a slightly different frequency crystal oscillator â an extra video card (which only worked in slot 7) was needed for color PAL graphics, since the simple tricks designer Steve Wozniak had used to generate a pseudo-NTSC signal with minimal hardware did not carry over to the more complex PAL system. In the Japanese version of the international Apple, the character ROM and the keyboard layout were changed to allow for Katakana writing (full Kanji support was clearly beyond the capabilities of the machine), but in most other countries the international Apple was sold with an unmodified American keyboard; thus the German model still lacked the umlauts, for example, and had a QWERTY layout instead of the standard German QWERTZ. For the most part, the Apple II Europlus and J-Plus were identical to the Apple II Plus and software compatibility was near 100%. Production of the Europlus ended in 1983.
ITT 2020[edit]
The ITT 2020 was an Apple II clone manufactured by ITT under license from Apple Computer (the first licensed clone), specifically for the European market.In contrast to the Apple II Europlus, the ITT 2020 supported full PAL color graphics
Bell & Howell[edit]
Bell & Howell Apple II Plus
The Apple II Plus was also sold by Bell & Howell specifically to educational markets under special license from Apple. The standard Apple II Plus was not UL-listed because the top could be opened; the B&H model was the same as the consumer version sold by Apple except that it came in a black case, which could not be opened as easily, and a special A/V package allowing it to be sold as audio/visual equipment. Bell & Howell packaged the unit with optional 'back packs' that offered various inputs and outputs for A/V equipment to easily interface with the II Plus.[5] This was the only black computer Apple would manufacture until the Macintosh TV in 1993.
Military applications[edit]
A TEMPEST-approved version of the Apple II Plus was created in 1980 by the Georgia Tech Research Institute for U.S. ArmyFORSCOM, and used as a component in the earliest versions of the Microfix system. Fielded in 1982, the Microfix system was the first tactical system using video disc (Laserdisc) map technology providing zoom and scroll over map imagery coupled with a point database of intelligence data such as order of battle, airfields, roadways, and bridges.[6][7][8]
Timeline of Apple II family modelsSee also[edit]References[edit]
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Apple_II_Plus&oldid=898600685'
An Apple II computer with an external modem
The Apple II (stylized as apple ][) is an 8-bithome computer and one of the world's first highly successful mass-produced microcomputer products,[2] designed primarily by Steve Wozniak (Steve Jobs oversaw the development of the Apple II's foam-molded plastic case[3] and Rod Holt developed the switching power supply).[4] It was introduced by Jobs and Wozniak at the 1977 West Coast Computer Faire and was the first consumer product sold by Apple Computer, Inc. It is the first model in a series of computers which were produced until Apple IIe production ceased in November 1993.[5] The Apple II marks Apple's first launch of a personal computer aimed at a consumer marketâbranded toward American households rather than businessmen or computer hobbyists.[6]
The three computers that Byte Magazine referred to as the '1977 Trinity' of home computing: the Commodore PET 2001, the Apple II, and the TRS-80 Model I.
Byte magazine referred to the Apple II, Commodore PET 2001 and the TRS-80 as the '1977 Trinity.'[7]The Apple II had the defining feature of being able to display color graphics, and this capability was the reason why the Apple logo was redesigned to have a spectrum of colors.
History[edit]
By 1976, Steve Jobs had convinced the product designer Jerry Manock (who had formerly worked at Hewlett Packard designing calculators) to create the 'shell' for the Apple IIâa smooth case inspired by kitchen appliances that would conceal the internal mechanics.[6] The earliest Apple IIs were assembled in Silicon Valley, and later in Texas;[8]printed circuit boards were manufactured in Ireland and Singapore. The first computers went on sale on June 10, 1977[9][10] with a MOS Technology 6502 microprocessor running at 1.023 MHz, two game paddles[11] (no longer bundled as of 1980 because they violated FCC regulations),[12] 4 KB of RAM, an audio cassette interface for loading programs and storing data, and the Integer BASIC programming language built into the ROMs. The video controller displays 24 lines by 40 columns of monochrome, uppercase-only (the original character set matches ASCII characters 20h to 5Fh) text on the screen, with NTSCcomposite video output suitable for display on a TV monitor, or on a regular TV set by way of a separate RF modulator. The original retail price of the computer was $1,298[13] (with 4 KB of RAM) and $2,638 (with the maximum 48 KB of RAM).[14] To reflect the computer's color graphics capability, the Apple logo on the casing has rainbow stripes,[15] which remained a part of Apple's corporate logo until early 1998. Perhaps most significantly, the Apple II was a catalyst for personal computers across many industries; it was responsible for opening the doors to software marketed at consumers.[6]
Overview[edit]
In the May 1977 issue of Byte, Steve Wozniak published a detailed description of his design; the article began, 'To me, a personal computer should be small, reliable, convenient to use, and inexpensive.'[16]
The Apple II used peculiar engineering shortcuts to save hardware and reduce costs, such as:
The text and graphics screens have a complex arrangement. For instance, the scanlines were not stored in sequential areas of memory. This complexity was reportedly due to Wozniak's realization that the method would allow for the refresh of the dynamic RAM as a side effect (as described above). This method had no cost overhead to have software calculate or look up the address of the required scanline and avoided the need for significant extra hardware. Similarly, in the high-resolution graphics mode, color is determined by pixel position and thus can be implemented in software, saving Wozniak the chips needed to convert bit patterns to colors. This also allowed for subpixel font rendering, since orange and blue pixels appear half a pixel-width farther to the right on the screen than green and purple pixels.[17]
The Apple II at first used data cassette storage like most other microcomputers of the time. In 1978, the company introduced an external â51â4-inch floppy disk drive, the Disk II, attached via a controller card that plugs into one of the computer's expansion slots (usually slot 6). The Disk II interface, created by Wozniak, is regarded as an engineering masterpiece for its economy of electronic components.[18][19]
The approach taken in the Disk II controller is typical of Wozniak's designs. With a few small-scale logic chips and a cheap PROM (programmable read-only memory), he created a functional floppy disk interface at a fraction of the component cost of standard circuit configurations.
Case design[edit]
Steve Jobs extensively pushed to give the Apple II a case that looked visually appealing and sellable to people outside of electronics hobbyists, rather than the generic wood and metal boxes typical of early microcomputers. The result was a futuristic-looking molded white plastic case. Jobs also paid close attention to the keyboard design and decided to use dark brown keycaps as it contrasted well with the case.
The first production Apple IIs had hand-molded cases; these had visible bubbles and other lumps in them from the imperfect plastic molding process, which was soon switched to machine molding. In addition, the initial case design had no vent openings, causing high heat buildup from the PCB and resulting in the plastic softening and sagging. Apple added vent holes to the case within three months of production; customers with the original case could have them replaced at no charge.
PCB revisions[edit]
The Apple II's PCB underwent several revisions as Steve Wozniak made modifications to it. The earliest version was known as Revision 0, and the first 6,000 units shipped used it. Later revisions added a color killer circuit to prevent color fringing when the computer was in text mode, as well as modifications to improve the reliability of cassette I/O. Revision 0 Apple IIs powered up in an undefined mode and had garbage on-screen, requiring the user to press Reset. This was eliminated on the later board revisions. Revision 0 Apple IIs could display only 4 colors in hi-res mode, but Wozniak was able to increase this to 6 hi-res colors on later board revisions.
The PCB had three RAM banks for a total of 24 RAM chips. Original Apple IIs had jumper switches to adjust the RAM size, and RAM configurations could be 4, 8, 12, 16, 20, 24, 32, 36, or 48k. The three smallest memory configurations used 4kx1 DRAMs, with larger ones using 16kx1 DRAMs, or mix of 4k and 16k banks (the chips in any bank have to be the same size). The early Apple II+ models retained this feature, but after a drop in DRAM prices, Apple redesigned the circuit boards without the jumpers so that only 16kx1 chips were supported. A few months later they started shipping all machines with a full 48 KB complement of DRAM.
Unlike most machines, all ICs on the Apple II PCB were socketed; although this cost more to manufacture and created the possibility of loose chips causing a system malfunction, it was considered preferable to make servicing and replacement of bad chips easier.
The Apple II PCB lacks any means of generating an IRQ, although expansion cards may generate one. Program code had to stop everything to perform any I/O task; like many of the computer's other idiosyncrasies, this was due to cost reasons and Steve Wozniak assuming interrupts were not needed for gaming or using the computer as a teaching tool.
Display and graphics[edit]
Color on the Apple II series uses a quirk of the NTSC television signal standard, which made color display relatively easy and inexpensive to implement. The original NTSC television signal specification was black-and-white. Color was added on later by adding a 3.58-MHz subcarrier signal that was partially ignored by black-and-white TV sets. Color is encoded based on the phase of this signal in relation to a reference color burst signal. The result is that the position, size, and intensity of a series of pulses define color information. These pulses can translate into pixels on the computer screen, with the possibility of exploiting composite artifact colors.
The Apple II display provides two pixels per subcarrier cycle. When the color burst reference signal is turned on and the computer attached to a color display, it can display green by showing one alternating pattern of pixels, magenta with an opposite pattern of alternating pixels, and white by placing two pixels next to each other. Blue and orange are available by tweaking the offset of the pixels by half a pixel-width in relation to the color-burst signal. The high-resolution display offers more colors by compressing more (and narrower) pixels into each subcarrier cycle.
The coarse, low-resolution graphics display mode works differently, as it can output a pattern of dots per pixel to offer more color options. These patterns are stored in the character generator ROM and replace the text character bit patterns when the computer is switched to low-res graphics mode. The text mode and low-res graphics mode use the same memory region and the same circuitry is used for both.
A single HGR page occupied 8k of RAM; in practice this meant that the user had to have at least 12k of total RAM to use HGR mode and 32k to use two pages. Early Apple II games from the 1977 to 79 period often ran only in text or low resolution mode to support users with small memory configurations; HGR not being near universally supported by games until 1980.
Sound[edit]
Rather than a dedicated sound-synthesis chip, the Apple II has a toggle circuit that can only emit a click through a built-in speaker or a line out jack; all other sounds (including two-, three- and, eventually, four-voice music and playback of audio samples and speech synthesis) are generated entirely by software that clicked the speaker at just the right times. Similar techniques are used for cassette storage: the cassette output works the same as the speaker, and the input is a simple zero-crossing detector that serves as a relatively crude (1-bit) audio digitizer. Routines in the ROM encode and decode data in frequency-shift keying for the cassette.
Programming languages[edit]
Initially, the Apple II was shipped with Integer BASIC encoded in the motherboard ROM chips. Written by Wozniak, the interpreter enabled users to write software applications without needing to purchase additional development utilities. Written with game programmers and hobbyists in mind, the language only supported the encoding of numbers in 16-bit integer format. Since it only supported integers between -32768 and +32767 (signed 16-bit integer), it was less suitable to business software and Apple soon received complaints from customers. Because Steve Wozniak was too busy developing the Disk II hardware, he did not have time to modify Integer BASIC for floating point support, so Apple instead licensed Microsoft's 6502 BASIC to create Applesoft BASIC. Disk users normally purchased a so-called Language Card which had Applesoft in ROM and sat below the Integer BASIC ROM in system memory. The user could switch between either BASIC by typing FP or INT at the BASIC prompt. Apple also offered a different version of Applesoft for cassette users which occupied low memory and was started by using the LOAD command in Integer BASIC.
As shipped, the machine incorporated a 'monitor' program which supported functions such as displaying and altering the contents of the computer's RAM memory in hexadecimal format, either one byte at a time or in blocks of 256 bytes at once. This feature enabled hackers to write and debug machine code programs without needing further development software. The computer powered on into the monitor ROM and the user was greeted with a * prompt. From there, he could enter BASIC by typing Ctrl+B, or he could load a machine language program from cassette. Disk software could be booted by typing Ctrl+P followed by 6, referring to Slot 6 which normally contained the Disk II controller.
A 6502 assembler was soon offered on disk, and later the UCSD compiler and operating system for the Pascal language were made available. The Pascal system required a 16 KB RAM card to be installed in the language card position (expansion slot 0) in addition to the full 48 KB of motherboard memory.
Manual[edit]
The first 1,000 or so Apple IIs shipped in 1977 with a 68-page mimeographed 'Apple II Mini Manual', hand-bound with brass paper fasteners. This was the basis for the Apple II Reference Manual, which was published in January 1978. All existing customers who sent in their warranty cards were sent free copies of the Red Book. The Apple II Reference Manual contained the complete schematic of the entire computer's circuitry and a complete source listing of the 'Monitor' ROM firmware that served as the machine's BIOS.
Third-party devices and applications[edit]
When the Apple II initially shipped in June 1977, no expansion cards were available for the slots. This meant that the user did not have any way of connecting a modem or a printer. One popular hack involved connecting a teletype machine to the cassette output.
Wozniak's open-architecture design and the Apple II's multiple expansion slots permitted a wide variety of third-party devices, including peripheral cards such as serial controllers, display controllers, memory boards, hard disks, networking components, and realtime clocks. There were plug-in expansion cardsâsuch as the Z-80 SoftCardâthat permitted the Apple to use the Z80 processor and run programs for the CP/M operating system,[20] including the dBase II database and the WordStar word processor. The Z80 card also allowed the connection to a modem and thereby to any networks that the user might have access to. In the early days, such networks were scarce. But they expanded significantly with the development of bulletin board systems in later years. There was also a third-party 6809 card that allowed OS-9 Level One to be run. Third-party sound cards greatly improved audio capabilities, allowing simple music synthesis and text-to-speech functions. Apple II accelerator cards doubled or quadrupled the computer's speed.
Early Apple IIs were often sold with a Sup'R'Mod, which allowed the composite video signal to be viewed on a television.
The Soviet Union reverse engineered the Apple II and its processor, producing a similar computer known as the AGAT. Roughly 12,000 were produced and it was widely used in Soviet Schools.[21]
Reception[edit]
Advertisement for the Apple II (1977)
Jesse Adams Stein wrote, 'As the first company to release a 'consumer appliance' micro-computer, Apple Computer offers us a clear view of this shift from a machine to an appliance.' But the company also had 'to negotiate the attitudes of its potential buyers, bearing in mind social anxieties about the uptake of new technologies in multiple contexts. The office, the home and the 'office-in-the-home' were implicated in these changing spheres of gender stereotypes and technological development.'[22] After seeing a crude, wire-wrapped prototype demonstrated by Wozniak and Steve Jobs in November 1976,[11]Byte predicted in April 1977 that the Apple II 'may be the first product to fully qualify as the 'appliance computer' ... a completed system which is purchased off the retail shelf, taken home, plugged in and used'. The computer's color graphics capability especially impressed the magazine.[23] The magazine published a favorable review of the computer in March 1978, concluding, 'For the user that wants color graphics, the Apple II is the only practical choice available in the 'appliance' computer class.'[11]
Personal Computer World in August 1978 also cited the color capability as a strength, stating that 'the prime reason that anyone buys an Apple II must surely be for the colour graphics'. While mentioning the 'oddity' of the artifact colors that produced output 'that is not always what one wishes to do', it noted that 'no-one has colour graphics like this at this sort of price'. The magazine praised the sophisticated monitor software, user expandability, and comprehensive documentation. The author concluded that 'the Apple II is a very promising machine' which 'would be even more of a temptation were its price slightly lower ... for the moment, colour is an Apple II'.[24]
Although it sold well from the launch, the initial market was to hobbyists and computer enthusiasts. Sales expanded exponentially into the business and professional market when the spreadsheet program VisiCalc was launched in mid-1979. VisiCalc is credited as the defining killer app in the microcomputer industry.
During the first five years of operations, revenues doubled about every four months. Between September 1977 and September 1980, annual sales grew from $775,000 to $118 million.[25] During this period the sole products of the company were the Apple II and its peripherals, accessories, and software.
See also[edit]References[edit]
External links[edit]![]()
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Apple_II&oldid=903212876'
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