IBM
International Business Machines Corporation is an American multinational information technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the Computing-Tabulating-Recording Company and was renamed "International Business Machines" in 1924. IBM produces and sells computer hardware and software, provides hosting and consulting services in areas ranging from mainframe computers to nanotechnology. IBM is a major research organization, holding the record for most U. S. patents generated by a business for 26 consecutive years. Inventions by IBM include the automated teller machine, the floppy disk, the hard disk drive, the magnetic stripe card, the relational database, the SQL programming language, the UPC barcode, dynamic random-access memory; the IBM mainframe, exemplified by the System/360, was the dominant computing platform during the 1960s and 1970s. IBM has continually shifted business operations by focusing on higher-value, more profitable markets.
This includes spinning off printer manufacturer Lexmark in 1991 and the sale of personal computer and x86-based server businesses to Lenovo, acquiring companies such as PwC Consulting, SPSS, The Weather Company, Red Hat. In 2014, IBM announced that it would go "fabless", continuing to design semiconductors, but offloading manufacturing to GlobalFoundries. Nicknamed Big Blue, IBM is one of 30 companies included in the Dow Jones Industrial Average and one of the world's largest employers, with over 380,000 employees, known as "IBMers". At least 70% of IBMers are based outside the United States, the country with the largest number of IBMers is India. IBM employees have been awarded five Nobel Prizes, six Turing Awards, ten National Medals of Technology and five National Medals of Science. In the 1880s, technologies emerged that would form the core of International Business Machines. Julius E. Pitrap patented the computing scale in 1885. On June 16, 1911, their four companies were amalgamated in New York State by Charles Ranlett Flint forming a fifth company, the Computing-Tabulating-Recording Company based in Endicott, New York.
The five companies had offices and plants in Endicott and Binghamton, New York. C.. They manufactured machinery for sale and lease, ranging from commercial scales and industrial time recorders and cheese slicers, to tabulators and punched cards. Thomas J. Watson, Sr. fired from the National Cash Register Company by John Henry Patterson, called on Flint and, in 1914, was offered a position at CTR. Watson joined CTR as General Manager 11 months was made President when court cases relating to his time at NCR were resolved. Having learned Patterson's pioneering business practices, Watson proceeded to put the stamp of NCR onto CTR's companies, he implemented sales conventions, "generous sales incentives, a focus on customer service, an insistence on well-groomed, dark-suited salesmen and had an evangelical fervor for instilling company pride and loyalty in every worker". His favorite slogan, "THINK", became a mantra for each company's employees. During Watson's first four years, revenues reached $9 million and the company's operations expanded to Europe, South America and Australia.
Watson never liked the clumsy hyphenated name "Computing-Tabulating-Recording Company" and on February 14, 1924 chose to replace it with the more expansive title "International Business Machines". By 1933 most of the subsidiaries had been merged into one company, IBM. In 1937, IBM's tabulating equipment enabled organizations to process unprecedented amounts of data, its clients including the U. S. Government, during its first effort to maintain the employment records for 26 million people pursuant to the Social Security Act, the tracking of persecuted groups by Hitler's Third Reich through the German subsidiary Dehomag. In 1949, Thomas Watson, Sr. created IBM World Trade Corporation, a subsidiary of IBM focused on foreign operations. In 1952, he stepped down after 40 years at the company helm, his son Thomas Watson, Jr. was named president. In 1956, the company demonstrated the first practical example of artificial intelligence when Arthur L. Samuel of IBM's Poughkeepsie, New York, laboratory programmed an IBM 704 not to play checkers but "learn" from its own experience.
In 1957, the FORTRAN scientific programming language was developed. In 1961, IBM developed the SABRE reservation system for American Airlines and introduced the successful Selectric typewriter. In 1963, IBM employees and computers helped. A year it moved its corporate headquarters from New York City to Armonk, New York; the latter half of the 1960s saw IBM continue its support of space exploration, participating in the 1965 Gemini flights, 1966 Saturn flights and 1969 lunar mission. On April 7, 1964, IBM announced the first computer system family, the IBM System/360, it spanned the complete range of commercial and scientific applications from large to small, allowing companies for the first time to upgrade to models with greater computing capability without having to rewrite their applications. It was followed by the IBM System/370 in 1970. Together the
IBM Displaywriter System
The IBM Displaywriter System 6580 was a dedicated microcomputer-based word processing machine that IBM's Office Products Division introduced in June 1980. The system consisted of a central processing unit, based on the Intel 8086, in a desktop case, a monochrome CRT monitor atop the CPU, a detached keyboard, a detached dual disk drive that used 8-inch floppy disks, a detached daisy wheel printer; the system booted from an 8-inch floppy disk that stored IBM's internally developed word processing software. The operator stored the "documents" on additional diskettes. "A basic system — consisting of a display with a typewriter-like keyboard and a logic unit, a printer and a device to record and read diskettes capable of storing more than 100 pages of average text — cost $7,895 and leased for $275 a month." The basic word-processing software was Textpack E, with simple mail merge. Other options included multilingual dictionaries and reports; the Displaywriter's features were comparable to other dedicated word processing machines of its era.
The features included mail-merge, with fields designated as a02, a03, etc.. Elementary arithmetic could be applied to the fields; the basic IBM Displaywriter was a standalone system. An optional central storage and management unit was available, which permitted multiple Displaywriters to share storage and a printer. UCSD p-Systemoperating system and CP/M-86 were available for the Displaywriter System but were not its regular Operating System. Connections to other IBM systems included: IBM 3278 emulation program to attach to IBM 3274/3276 controllers, IBM 4321/4331, or IBM 4701. IBM 3277 emulation program to attach to 3274 controllers. Connection to IBM 8100 systems which use DPCX/DOSF; because of Displaywriter's popularity, IBM produced DisplayWrite software for the IBM Personal Computer, with a similar user interface and equivalent to Textpack 4. Media related to IBM Displaywriter System at Wikimedia Commons
Microcomputer
A microcomputer is a small inexpensive computer with a microprocessor as its central processing unit. It includes a microprocessor and minimal input/output circuitry mounted on a single printed circuit board. Microcomputers became popular in the 1970s and 1980s with the advent of powerful microprocessors; the predecessors to these computers and minicomputers, were comparatively much larger and more expensive. Many microcomputers are personal computers; the abbreviation micro was common during the 1970s and 1980s, but has now fallen out of common usage. The term microcomputer came into popular use after the introduction of the minicomputer, although Isaac Asimov used the term in his short story "The Dying Night" as early as 1956. Most notably, the microcomputer replaced the many separate components that made up the minicomputer's CPU with one integrated microprocessor chip; the French developers of the Micral N filed their patents with the term "Micro-ordinateur", a literal equivalent of "Microcomputer", to designate a solid state machine designed with a microprocessor.
In the USA, the earliest models such as the Altair 8800 were sold as kits to be assembled by the user, came with as little as 256 bytes of RAM, no input/output devices other than indicator lights and switches, useful as a proof of concept to demonstrate what such a simple device could do. However, as microprocessors and semiconductor memory became less expensive, microcomputers in turn grew cheaper and easier to use: Increasingly inexpensive logic chips such as the 7400 series allowed cheap dedicated circuitry for improved user interfaces such as keyboard input, instead of a row of switches to toggle bits one at a time. Use of audio cassettes for inexpensive data storage replaced manual re-entry of a program every time the device was powered on. Large cheap arrays of silicon logic gates in the form of read-only memory and EPROMs allowed utility programs and self-booting kernels to be stored within microcomputers; these stored programs could automatically load further more complex software from external storage devices without user intervention, to form an inexpensive turnkey system that does not require a computer expert to understand or to use the device.
Random access memory became cheap enough to afford dedicating 1-2 kilobytes of memory to a video display controller frame buffer, for a 40x25 or 80x25 text display or blocky color graphics on a common household television. This replaced the slow and expensive teletypewriter, common as an interface to minicomputers and mainframes. All these improvements in cost and usability resulted in an explosion in their popularity during the late 1970s and early 1980s. A large number of computer makers packaged microcomputers for use in small business applications. By 1979, many companies such as Cromemco, Processor Technology, IMSAI, North Star Computers, Southwest Technical Products Corporation, Ohio Scientific, Altos Computer Systems, Morrow Designs and others produced systems designed either for a resourceful end user or consulting firm to deliver business systems such as accounting, database management, word processing to small businesses; this allowed businesses unable to afford leasing of a minicomputer or time-sharing service the opportunity to automate business functions, without hiring a full-time staff to operate the computers.
A representative system of this era would have used an S100 bus, an 8-bit processor such as an Intel 8080 or Zilog Z80, either CP/M or MP/M operating system. The increasing availability and power of desktop computers for personal use attracted the attention of more software developers. In time, as the industry matured, the market for personal computers standardized around IBM PC compatibles running DOS, Windows. Modern desktop computers, video game consoles, tablet PCs, many types of handheld devices, including mobile phones, pocket calculators, industrial embedded systems, may all be considered examples of microcomputers according to the definition given above. Everyday use of the expression "microcomputer" has declined from the mid-1980s and has declined in commonplace usage since 2000; the term is most associated with the first wave of all-in-one 8-bit home computers and small business microcomputers. Although, or because, an diverse range of modern microprocessor-based devices fit the definition of "microcomputer", they are no longer referred to as such in everyday speech.
In common usage, "microcomputer" has been supplanted by the term "personal computer" or "PC", which specifies a computer, designed to be used by one individual at a time, a term first coined in 1959. IBM first promoted the term "personal computer" to differentiate themselves from other microcomputers called "home computers", IBM's own mainframes and minicomputers. However, following its release, the IBM PC itself was imitated, as well as the term; the component parts were available to producers and the BIOS was reverse engineered through cleanroom design techniques. IBM PC compatible "clones" became commonplace, the terms "personal computer", "PC", stuck with the general public specifically for a DOS or Windows-compatible computer. Monitors and other devices for inpu
WYSIWYG
WYSIWYG is an acronym for "what you see is what you get". In computing, a WYSIWYG editor is a system in which content can be edited in a form resembling its appearance when printed or displayed as a finished product, such as a printed document, web page, or slide presentation. WYSIWYG implies a user interface that allows the user to view something similar to the end result while the document is being created. In general, WYSIWYG implies the ability to directly manipulate the layout of a document without having to type or remember names of layout commands; the actual meaning depends on the user's perspective, e.g. In presentation programs, compound documents, web pages, WYSIWYG means the display represents the appearance of the page displayed to the end-user, but does not reflect how the page will be printed unless the printer is matched to the editing program, as it was with the Xerox Star and early versions of the Apple Macintosh. In word processing and desktop publishing applications, WYSIWYG means that the display simulates the appearance and represents the effect of fonts and line breaks on the final pagination using a specific printer configuration, so that, for example, a citation on page 1 of a 500-page document can refer to a reference three hundred pages later.
WYSIWYG describes ways to manipulate 3D models in stereo-chemistry, computer-aided design, 3D computer graphics. Modern software does a good job of optimizing the screen display for a particular type of output. For example, a word processor is optimized for output to a typical printer; the software emulates the resolution of the printer in order to get as close as possible to WYSIWYG. However, not the main attraction of WYSIWYG, the ability of the user to be able to visualize what they are producing. In many situations, the subtle differences between what the user sees and what the user gets are unimportant. In fact, applications may offer multiple WYSIWYG modes with different levels of "realism", including A composition mode, in which the user sees something somewhat similar to the end result, but with additional information useful while composing, such as section breaks and non-printing characters, uses a layout, more conducive to composing than to layout. A layout mode, in which the user sees something similar to the end result, but with some additional information useful in ensuring that elements are properly aligned and spaced, such as margin lines.
A preview mode, in which the application attempts to present a representation, as close to the final result as possible. Before the adoption of WYSIWYG techniques, text appeared in editors using the system standard typeface and style with little indication of layout. Users were required to enter special non-printing control codes to indicate that some text should be in boldface, italics, or a different typeface or size. In this environment there was little distinction between text editors and word processors; these applications used an arbitrary markup language to define the codes/tags. Each program had its own special way to format a document, it was a difficult and time-consuming process to change from one word processor to another; the use of markup tags and codes remains popular today in some applications due to their ability to store complex formatting information. When the tags are made visible in the editor, they occupy space in the unformatted text and so disrupt the desired layout and flow.
Bravo, a document preparation program for the Alto produced at Xerox PARC by Butler Lampson, Charles Simonyi and colleagues in 1974, is considered the first program to incorporate WYSIWYG technology, displaying text with formatting. The Alto monitor was designed so that one full page of text could be seen and printed on the first laser printers; when the text was laid out on the screen, 72 PPI font metric files were used, but when printed 300 PPI files were used—thus one would find characters and words off, a problem that continues to this day. Bravo was released commercially and the software included in the Xerox Star can be seen as a direct descendant of it. In parallel with but independent of the work at Xerox PARC, Hewlett Packard developed and released in late 1978 the first commercial WYSIWYG software application for producing overhead slides or what today are called presentation graphics; the first release, named BRUNO, ran on the HP 1000 minicomputer taking advantage of HP's first bitmapped computer terminal the HP 2640.
BRUNO was ported to the HP-3000 and re-released as "HP Draw". By 1981 MicroPro advertised that its WordStar word processor had WYSIWYG, but its display was limited to displaying styled text in WYSIWYG fashion. In 1983 the Weekly Reader advertised its Stickybear educational software with the slogan "what you see is what you get", with photographs of its Apple II graphics, but home computers of the 1970s and early 1980s lacked the sophisticated graphics capabilities necessary to display WYSIWYG documents, meaning that such applications were confined to limited-purpose, high-end workstations that were too expensive for the general public to afford. Towards the mid-1980s, things began to change. Improving technology allowed the production of cheaper bitmapped displays, WYSIWYG software started to appear for more popular computers, including LisaWrite
IBM Personal Computer
The IBM Personal Computer known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, was introduced on August 12, 1981, it was created by a team of engineers and designers under the direction of Don Estridge of the IBM Entry Systems Division in Boca Raton, Florida. The generic term "personal computer" was in use years before 1981, applied as early as 1972 to the Xerox PARC's Alto, but because of the success of the IBM Personal Computer, the term "PC" came to mean more a desktop microcomputer compatible with IBM's Personal Computer branded products. Since the machine was based on open architecture, within a short time of its introduction, third-party suppliers of peripheral devices, expansion cards, software proliferated. "IBM compatible" became an important criterion for sales growth. International Business Machines, one of the world's largest companies, had a 62% share of the mainframe computer market in 1982. In the late 1970s the new personal computer industry was dominated by the Commodore PET, Atari 8-bit family, Apple II, Tandy Corporation's TRS-80, various CP/M machines.
With $150 million in sales by 1979 and projected annual growth of more than 40% in the early 1980s, the microcomputer market was large enough for IBM's attention. Other large technology companies such as Hewlett-Packard, Texas Instruments, Data General had entered it, some large IBM customers were buying Apples, so the company saw introducing its own personal computer as both an experiment in a new market and a defense against rivals and small. In 1980 and 1981 rumors spread of an IBM personal computer a miniaturized version of the IBM System/370, while Matsushita acknowledged that it had discussed with IBM the possibility of manufacturing a personal computer for the American company; the Japanese project, codenamed "Go", ended before the 1981 release of the American-designed IBM PC codenamed "Chess", but two simultaneous projects further confused rumors about the forthcoming product. Data General and TI's small computers were not successful, but observers expected AT&T to soon enter the computer industry, other large companies such as Exxon, Montgomery Ward and Sony were designing their own microcomputers.
Xerox produced the 820 to introduce a personal computer before IBM, becoming the second Fortune 500 company after Tandy to do so, had its Xerox PARC laboratory's sophisticated technology. Whether IBM had waited too long to enter an industry in which Tandy and others were successful was unclear. An observer stated that "IBM bringing out a personal computer would be like teaching an elephant to tap dance." Successful microcomputer company Vector Graphic's fiscal 1980 revenue was $12 million. A single IBM computer in the early 1960s cost as much as $9 million, occupied one quarter acre of air-conditioned space, had a staff of 60 people; the "Colossus of Armonk" only sold through its own sales force, had no experience with resellers or retail stores, did not introduce the first product designed to work with non-IBM equipment until 1980. Another observer claimed that IBM made decisions so that, when tested, "what they found is that it would take at least nine months to ship an empty box"; as with other large computer companies, its new products required about four to five years for development.
IBM had to learn how to develop, mass-produce, market new computers. While the company traditionally let others pioneer a new market—IBM released its first commercial computer a year after Remington Rand's UNIVAC in 1951, but within five years had 85% of the market—the personal-computer development and pricing cycles were much faster than for mainframes, with products designed in a few months and obsolete quickly. Many in the microcomputer industry resented IBM's power and wealth, disliked the perception that an industry founded by startups needed a latecomer so staid that it had a strict dress code and employee songbook; the potential importance to microcomputers of a company so prestigious, that a popular saying in American companies stated "No one got fired for buying IBM", was nonetheless clear. InfoWorld, which described itself as "The Newsweekly for Microcomputer Users", stated that "for my grandmother, for millions of people like her, IBM and computer are synonymous". Byte stated in an editorial just before the announcement of the IBM PC: Rumors abound about personal computers to come from giants such as Digital Equipment Corporation and the General Electric Company.
But there is no contest. IBM's new personal computer... is far and away the media star, not because of its features, but because it exists at all. When the number eight company in the Fortune 500 enters the field, news... The influence of a personal computer made by a company whose name has come to mean "computer" to most of the world is hard to contemplate; the editorial acknowledged that "some factions in our industry have looked upon IBM as the'enemy'", but concluded with optimism: "I want to see personal computing take a giant step." Desktop sized programmable calculators by HP had evolved into the HP 9830 BASIC language computer by 1972. In 1972–1973 a team led by Dr. Paul Friedl at the IBM Los Gatos Scientific Center developed a portable computer prototype called SCAMP (Special Computer APL Machine Po
IBM Z
IBM Z is a family name used by IBM for all of its non-POWER mainframe computers from the Z900 on. In July 2017, with another generation of products, the official family was changed to IBM Z from IBM z Systems; the zSeries, zEnterprise, System z and IBM Z families were named for their availability – z stands for zero downtime. The systems are built with spare components capable of hot failovers to ensure continuous operations; the IBM Z family maintains full backward compatibility. In effect, current systems are the direct, lineal descendants of System/360, announced in 1964, the System/370 from the 1970s. Many applications written for these systems can still run unmodified on the newest IBM Z system over five decades later. Virtualization is required by default on IBM Z systems. First layer virtualization is provided by the Processor Resource and System Manager to deploy one or more Logical Partitions; each LPAR supports a variety of operating systems. A hypervisor called z/VM can be run as the second layer virtualization in LPARs to create as many virtual machines as there are resources assigned to the LPARs to support them.
The first layer of IBM Z virtualization allows a z machine to run a limited number of LPARs. These can be considered virtual "bare metal" servers because PR/SM allows CPUs to be dedicated to individual LPARs. Z/VM LPARs allocated within PR/SM LPARs can run a large number of virtual machines as long as there are adequate CPU, I/O resources configured with the system for the desired performance and throughput. IBM Z's PR/SM and hardware attributes allow compute resources to be dynamically changed to meet workload demands. CPU and memory resources can be non-disruptively added to the system and dynamically assigned and used by LPARs. I/O resources such as IP and SAN ports can be added dynamically, they are shared across all LPARs. The hardware component that provides this capability is called the Channel Subsystem; each LPAR can be configured to either "see" or "not see" the virtualized I/O ports to establish desired "shareness" or isolation. This virtualization capability allows significant reduction in I/O resources because of its ability to share them and drive up utilization.
PR/SM on IBM Z has earned Common Criteria Evaluation Assurance Level 5+ security certification, z/VM has earned Common Criteria EAL4+ certification. The KVM hypervisor from Linux has been ported. Since the move away from the System/390 name, a number of IBM Z models have been released; these can be grouped into families with similar architectural characteristics. IBM z14 ZR1 single-frame mainframe introduced on April 10, 2018 IBM z14 mainframe introduced on July 17, 2017 Official IBM z14 mainframe product page IBM Redbooks z14 technical guide z Systems z13s, introduced on February 17 2016 z Systems z13, introduced on January 13, 2015 The IBM zEnterprise System, announced in July 2010, with the z196 model, is designed to offer both mainframe and distributed server technologies in an integrated system; the zEnterprise System consists of three components. First is a System z server. Second is the IBM zEnterprise BladeCenter Extension. Last is the management layer, IBM zEnterprise Unified Resource Manager, which provides a single management view of zEnterprise resources.
The zEnterprise is designed to extend mainframe capabilities – management efficiency, dynamic resource allocation, serviceability – to other systems and workloads running on AIX on POWER7, Microsoft Windows or Linux on x86. The zEnterprise BladeCenter Extension is an infrastructure component that hosts both general purpose blade servers and appliance-like workload optimizers which can all be managed as if they were a single mainframe; the zBX supports a private high speed internal network that connects it to the central processing complex, which reduces the need for networking hardware and provides inherently high security. The IBM zEnterprise Unified Resource Manager integrates the System z and zBX resources as a single virtualized system and provides unified and integrated management across the zEnterprise System, it can identify system bottlenecks or failures among disparate systems and if a failure occurs it can dynamically reallocate system resources to prevent or reduce application problems.
The Unified Resource Manager provides energy monitoring and management, resource management, increased security, virtual networking, information management from a single user interface. Highlights of the original zEnterprise z196 include: BladeCenter Extension and Unified Resource Manager Up to 80 central processors 60% higher capacity than the z10 Twice the memory capacity 5.2 GHz quad-core chipsThe newest zEnterprise, the EC12, was announced in August 2012, included: Up to 101 central processors 50% higher capacity than the z196 Transactional Execution 5.5 GHz hex-core chips Flash Express – integrated SSDs which improve paging and certain other I/O performanceOn April 8, 2014, in honor of the 50th anniversary of the System/360 mainframe, IBM announced the release of its first converged infrastructure solution based on mainframe technology. Dubbed the IBM Enterprise Cloud System, this new offering combines IBM mainframe hardwa
IBM PCjr
The IBM PCjr is a home computer, produced and marketed by IBM from March 1984 to May 1985. The PCjr was positioned as a complement to the successful IBM Personal Computer, competing with other home computers such as the Apple II series and the Commodore 64, it retains the IBM PC's 8088 CPU and BIOS interface, but provides enhanced graphics and sound capabilities over the original IBM PC, ROM cartridge slots, joystick ports, an infrared wireless keyboard. The PCjr supports expansion via "sidecar" modules. New software such as King's Quest. Despite widespread anticipation, the PCjr's launch was unsuccessful. IBM's inexperience with the consumer market led to unclear positioning, with analysts believing that IBM was unsuccessful at justifying the PCjr's higher cost in comparison to competitors such as the Commodore 64 and Apple II, it is only IBM compatible, so compatibility with existing PC software such as the killer app Lotus 1-2-3 was not guaranteed. The PCjr's chiclet keyboard was criticized for its poor quality, with critics stating that it was unsuitable for extended use such as word processing.
The PCjr's expandability was limited, it was offered with up to 128 KB of RAM only, insufficient for many IBM PC programs. The New York Times stated that the PCjr was incapable of "serious business computing". Consumers were more interested in Apple's newly-unveiled Macintosh than the PCjr. Apple cut the price of the IIe and introduced the IIc as a direct competitor, with advertising promoting its compatibility with existing Apple II software. In 1984, IBM offered free replacement keyboards with a more traditional design, a new 512 KB RAM upgrade. A large advertising campaign promoted the PCjr's compatibility with "over 1000" of the most popular IBM PC applications, new discounted pricing and other bundle offers. By January 1985, when the discounts ended, IBM had sold 250,000 PCjr computers, with 200,000 in the fourth quarter of 1984 alone. Unable to sell the computer without discounts, IBM discontinued the PCjr in March 1985, IBM would not produce a home-oriented computer until the PS/1 in 1990.
Time described the PCjr as "one of the biggest flops in the history of computing", with critics comparing it to the Ford Edsel and New Coke. The Tandy Corporation's clone of the PCjr, the Tandy 1000, was a more successful product, due to its cheaper cost, easier expandability, wider PC compatibility than the PCjr; the graphics and sound specifications of the PCjr became more synonymous with Tandy as a result, leading to computers and software supporting them being referred to as "Tandy compatible". Announced November 1, 1983, first shipped in late January 1984, the PCjr—nicknamed "Peanut" before its debut—came in two models: the 4860-004, with 64 KB of memory, priced at US$669, it was manufactured for IBM in Tennessee by Teledyne. The PCjr promised a high degree of compatibility with the IBM PC, a popular business computer, in addition to offering built-in color graphics and 3 voice sound, better than the standard PC-speaker sound and color graphics of the standard IBM PC and compatibles of the day.
The PCjr is the first PC compatible machine, expressly designed to support page flipping for graphics operations. Since the PCjr uses system RAM to store video content, the location of this storage area can be changed, it can perform flicker-free animation and other effects that are difficult or impossible to produce on contemporary PC clones. Unlike the standard IBM PC, the PCjr has onboard video hardware, it is an improved subset of the CGA standard. The four CGA video modes are supported in addition to three new graphics modes; the 80x25 text mode, 320x200x16, 640x200x4 modes are referred to in IBM's documentation as "the high bandwidth modes". The PCjr has a composite video out and can support artifact colors on a TV or composite monitor much like the CGA cards, although the colors are different; the PCjr has palette registers which allow the colors to be redefined for any of the available 16--this feature was retained in EGA and VGA cards. When the BIOS is used to set a video mode, it always sets up the PCjr palette table to emulate the CGA color palette for that mode.
Programs written to use PCjr graphics can subsequently reprogram the palette table to use any colors desired. Palette changes must be made during horizontal or vertical blanking periods of a video frame in order to avoid corrupting the display. However, the provision of a vertical retrace interrupt simplifies this and makes seamless page-flipping much easier. Although standard PC video cards had a flag to indicate that the vertical retrace was in progress, the PCjr added for the first time the ability to generate raster or VBLANK interrupts on IRQ 5; this allowed the use of mixed video modes. The PCjr video subsystem has a little-known graphics blink feature, which toggles the palette between the first and second groups of eight palette registers at the same rate used for the text blink feature, a palette bit-masking feature that could be used to switch between palette subsets without reprogramming palette registers, by forcing one or more bits of each pixel value to zero before the value is used to look up the color in the pale
