Apple II series

tag:blogger.com,1999:blog-3509381421021191501.post-87119998979741642112007-05-29T03:24:00.000-07:002007-05-29T03:25:17.711-07:00Apple II seriesThe Apple II (sometimes written as Apple ][ or Apple //) was the first popular microcomputer manufactured by Apple. Its direct ancestor was the Apple I, a limited production circuit board computer for electronics hobbyists which pioneered many features that made the Apple II a commercial success. Introduced at the West Coast Computer Faire in 1977, the Apple II was one of the very first and most successful personal computers. A number of different models were sold, and the most popular model was manufactured with relatively minor changes into the 1990s. By the end of its production in 1993, somewhere between five and six million Apple II series computers (including approximately 1.25 million Apple IIgs models) had been produced. Throughout the 1980s and much of the 1990s, the Apple II was the de facto standard computer in American education; some of them are still operational in classrooms today. The Apple II was popular with business users as well as with families and schools, particularly after the release of the first-ever computer spreadsheet, VisiCalc, which initially ran only on the Apple II. The Apple II was originally running only the built-in BASIC interpreter contained in ROM. Apple DOS was added to support the diskette drive; the last version was "Apple DOS 3.3". Apple DOS was superseded by ProDOS to support a hierarchical filesystem and larger storage devices. Using a diskette or hard-disk, the Apple II could also load the UCSD Pascal operating system. UCSD binaries are compatible with a large number of other computers, including the IBM-PC. Using a Z80 interface the Apple II could run the popular Wordstar and dBase software under the CP/M operating system. Apple's Macintosh product line finally eclipsed the Apple II series in the early 1990s. Even after the introduction of the Macintosh, the Apple II had remained Apple's primary source of revenue for years: the Apple II and its associated community of third-party developers and retailers were once a billion-dollar-a-year industry. The IIGS model was sold through to the end of 1992. The IIe model was removed from the product line on October 15, 1993, ending an era. Design Unlike any other microcomputer before it, the Apple II looked more like an appliance than a piece of electronic equipment. This was a computer that would not seem out of place in the home, on a manager's desk or in a classroom. The lid popped easily off the beige plastic case, allowing access to the entire internals of the computer, including the motherboard with eight expansion slots and RAM sockets, which could hold up to 48 KiB of memory. The Apple II had color and high-resolution graphics modes, sound capabilities and two built-in BASIC programming languages, Applesoft and Integer. Compared with earlier microcomputers, these features were well-documented and easy to learn. The Apple II sparked the beginning of the personal computer revolution, as it was targeted for the masses rather than just hobbyists and engineers; its introduction and subsequent popularity also greatly influenced most of the microcomputers that followed it. "VanLOVEs Apple Handbook" and "The Apple Educators Guide" by Gerald VanDiver and Rolland Love reviewed more than 1500 software programs that the Apple II series could use.. The Apple dealer network used this book to emphasize the growing software developer base in education and personal use.The books became part of the Apple program and became the first book on database. Models See also the Timeline of computing article. Apple II The first Apple II computers went on sale on June 5, 1977 with a MOS Technology 6502 microprocessor running at 1 MHz, 4 KiB 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 displayed 24 lines by 40 columns of upper-case-only text on the screen, with NTSC composite video output suitable for display on a monitor, or on a TV set by way of an RF modulator. The original retail price of the computer was US$1298 (with 4 KiB of RAM) and US$2638 (with the maximum 48 KiB of RAM). To reflect the computer's color graphics capability, the Apple logo on the casing was represented using rainbow stripes,[1] which remained a part of Apple's corporate logo until early 1998. The earliest Apple IIs were assembled in Silicon Valley, and later in Texas [2]; printed circuit boards were manufactured in Ireland and Singapore. In 1978, an external 5¼-inch floppy disk drive, the Disk II, attached via a controller card that plugged into one of the computer's expansion slots (usually slot 6), was used for data storage and retrieval to replace cassettes. The Disk II interface, created by Steve Wozniak, was regarded as an engineering masterpiece at the time for its economy of components. [3] [4] While other controllers had dozens of chips for synchronizing data I/O with disk rotation, seeking the head to the appropriate track, and encoding the data into magnetic pulses, Wozniak's controller card had few chips; instead, the Apple DOS used software to perform these functions. The Group Code Recording used by the controller was simpler and easier to implement in software than the more common MFM. In the end, the low chip count of the controller contributed to making Apple's Disk II the first affordable floppy drive system for personal computers. As a side effect, Woz's scheme made it easy for proprietary software developers to copy-protect the media on which their software shipped by changing the low-level sector format or stepping the drive's head between the tracks; inevitably, other companies eventually sold software to foil this protection. Another Wozniak optimization allowed him to omit Shugart's Track-0 sensor. When the Operating System wants to go to track 0, the controller simply moves toward the next-lower-numbered track, and keeps doing it until it can't go any further: this is presumed to be track 0. This process, called "recallibration", made a loud buzzing (rapid mechanical chattering) sound that often frightened Apple novices. The approach taken in the Disk II controller was typical of Wozniak's design sensibility. The Apple II was full of clever engineering tricks to save hardware and reduce costs. For example, taking advantage of the way that 6502 instructions only access memory every other clock cycle, the video generation circuitry's memory access on the otherwise unused cycles avoided memory contention issues and also eliminated the need for a separate refresh circuit for the DRAM chips. Rather than using a complex analog-to-digital circuit to read the outputs of the game controller, Wozniak used a simple timer circuit whose period was proportional to the resistance of the game controller, and used a software loop to measure the timer. The text and graphics screens had a somewhat outdated arrangement (the scanlines were not stored in sequential areas of memory) which was reputedly due to Woz's realization that doing it that way would save a chip; it was less expensive to have software calculate or look up the address of the required scanline than to include the extra hardware. Similarly, in the high-resolution graphics mode, color was determined by pixel position and could thus be implemented in software, saving Woz the chips needed to convert bit patterns to colors. The epitome of the Apple II design philosophy was the Apple II sound circuitry. Rather than having a dedicated sound-synthesis chip, the Apple II had a toggle circuit that could only emit a click through a built-in speaker; all other sounds (including two, three and, eventually, four-voice music and playback of audio samples and speech synthesis) were generated entirely by clever software that clicked the speaker at just the right times. Not for nearly a decade would an Apple II be released with a dedicated sound chip. Similar techniques were used for cassette storage: the cassette output worked the same as the speaker, and the input was a simple zero-crossing detector that served as a relatively crude (1-bit) audio digitizer. Routines in the ROM were used to encode and decode data in frequency shift keying for the cassette. Wozniak's open design and the Apple II's multiple expansion slots permitted a wide variety of third-party devices to expand the capabilities of the machine. Apple II peripheral cards such as Serial controllers, improved display controllers, memory boards, hard disks, and networking components were available for this system in its day. There were emulator cards, such as the Z80 card that permitted the Apple to switch to the Z80 processor and run a multitude of programs developed under the CP/M operating system, including the dBase II database and the WordStar word processor. (At one point in the mid-1980's, more than half the machines running CP/M were Apple II's with Z80 cards.)There was also a third-party 6809 card that would allow OS-9 Level One to be run. The Mockingboard sound card greatly improved the audio capabilities of the Apple, with simple music synthesis and text-to-speech functions. Eventually, Apple II accelerator cards were created to double or quadruple the computer's speed. Perfect Domainhttp://www.blogger.com/profile/12404243111659601804noreply@blogger.com