A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers. It uses a computer network to spread itself, relying on security failures on the target computer to access it. Worms always cause at least some harm to the network if only by consuming bandwidth, whereas viruses always corrupt or modify files on a targeted computer. Many worms are designed only to spread, do not attempt to change the systems they pass through. However, as the Morris worm and Mydoom showed these "payload-free" worms can cause major disruption by increasing network traffic and other unintended effects; the actual term "worm" was first used in The Shockwave Rider. In that novel, Nichlas Haflinger designs and sets off a data-gathering worm in an act of revenge against the powerful men who run a national electronic information web that induces mass conformity. "You have the biggest-ever worm loose in the net, it automatically sabotages any attempt to monitor it...
There's never been a worm with that tough a head or that long a tail!"On November 2, 1988, Robert Tappan Morris, a Cornell University computer science graduate student, unleashed what became known as the Morris worm, disrupting a large number of computers on the Internet, guessed at the time to be one tenth of all those connected. During the Morris appeal process, the U. S. Court of Appeals estimated the cost of removing the virus from each installation at between $200 and $53,000. Morris himself became the first person tried and convicted under the 1986 Computer Fraud and Abuse Act. Any code designed to do more than spread the worm is referred to as the "payload". Typical malicious payloads might delete files on a host system, encrypt files in a ransomware attack, or exfiltrate data such as confidential documents or passwords; the most common payload for worms is to install a backdoor. This allows the computer to be remotely controlled by the worm author as a "zombie". Networks of such machines are referred to as botnets and are commonly used for a range of malicious purposes, including sending spam or performing DoS attacks.
Worms spread by exploiting vulnerabilities in operating systems. Vendors with security problems supply regular security updates, if these are installed to a machine the majority of worms are unable to spread to it. If a vulnerability is disclosed before the security patch released by the vendor, a zero-day attack is possible. Users need to be wary of opening unexpected email, should not run attached files or programs, or visit web sites that are linked to such emails. However, as with the ILOVEYOU worm, with the increased growth and efficiency of phishing attacks, it remains possible to trick the end-user into running malicious code. Anti-virus and anti-spyware software are helpful, but must be kept up-to-date with new pattern files at least every few days; the use of a firewall is recommended. In the April–June 2008 issue of IEEE Transactions on Dependable and Secure Computing, computer scientists described a new and effective way to combat internet worms; the researchers discovered how to contain worms that scanned the Internet randomly, looking for vulnerable hosts to infect.
They found that the key was to use software to monitor the number of scans that machines on a network send out. When a machine started to send out too many scans, it was a sign that it has been infected, which allowed administrators to take it off line and check it for malware. In addition, machine learning techniques can be used to detect new worms, by analyzing the behavior of the suspected computer. Users can minimize the threat posed by worms by keeping their computers' operating system and other software up to date, avoiding opening unrecognized or unexpected emails and running firewall and antivirus software. Mitigation techniques include: ACLs in routers and switches Packet-filters TCP Wrapper/ACL enabled network service daemons Nullroute Beginning with the first research into worms at Xerox PARC, there have been attempts to create useful worms; those worms allowed testing by John Shoch and Jon Hupp of the Ethernet principles on their network of Xerox Alto computers. The Nachi family of worms tried to download and install patches from Microsoft's website to fix vulnerabilities in the host system—by exploiting those same vulnerabilities.
In practice, although this may have made these systems more secure, it generated considerable network traffic, rebooted the machine in the course of patching it, did its work without the consent of the computer's owner or user. Regardless of their payload or their writers' intentions, most security experts regard all worms as malware. Several worms, like XSS worms, have been written to research. For example, the effects of changes in social activity or user behavior. One study proposed what seems to be the first computer worm that operates on the second layer of the OSI model, it utilizes topology information such as Content-addressable memory tables and Spanning Tree information stored in switches to propagate and probe for vulnerable nodes until the enterprise network is covered. Botnet Code Shikara Computer and network surveillance Computer virus Email spam Father Christmas Self-replicating machine Timeline of computer viruses and worms Trojan horse XSS worm Zombie Malware Guide – Guide for understanding and preventing worm infections on Vernalex.com.
"The'Worm' Programs – Early Experience with a Distributed Computation", John Shoch and Jon Hupp, Communications of the ACM, Volum
The Wii is a home video game console released by Nintendo on November 19, 2006. As a seventh-generation console, the Wii competed with Microsoft's Xbox 360 and Sony's PlayStation 3. Nintendo states; as of the first quarter of 2016, the Wii led its generation over the PlayStation 3 and Xbox 360 in worldwide sales, with more than 101 million units sold. The Wii introduced the Wii Remote controller, which can be used as a handheld pointing device and which detects movement in three dimensions; the console runs games supplied on Wii optical discs. It supported the now discontinued WiiConnect24 service, which enabled Wii to receive messages and updates over the Internet while in standby mode. Like other seventh-generation consoles it supported a service, called "Virtual Console", that downloaded emulated games from past Nintendo consoles, support for online video streaming such as BBC iPlayer, other services provided by Nintendo over the Internet. Internet services were withdrawn. Wii Points could no longer be purchased after March 2018, could not be used and were permanently lost from 31 January 2019.
The Wii succeeded the GameCube. Nintendo first spoke of the console at the E3 2004 press conference and unveiled it at E3 2005. Nintendo CEO Satoru Iwata revealed a prototype of the controller at the September 2005 Tokyo Game Show. At E3 2006, the console won the first of several awards. By December 8, 2006, it had completed its launch in the four key markets. Models are no longer compatible with Nintendo GameCube. In late 2011, Nintendo released a reconfigured model, the "Wii Family Edition", not released in Japan; the Wii Mini, Nintendo's first major console redesign since the compact SNES, succeeded the standard Wii model and was released first in Canada on December 7, 2012. The Wii Mini can only play Wii optical discs, as it has neither GameCube compatibility nor any networking capabilities; the Wii's successor, the Wii U, was released on November 18, 2012. On October 20, 2013, Nintendo confirmed it had discontinued production of the Wii in Japan and Europe; the console was conceived in 2001.
According to an interview with Nintendo game designer Shigeru Miyamoto, the concept involved focusing on a new form of player interaction. "The consensus was. Too many powerful consoles can't coexist. It's like having only ferocious dinosaurs, they might fight and hasten their own extinction."In 2003, game engineers and designers were brought together to develop the concept further. By 2005 the controller interface had taken form, but a public showing at that year's Electronic Entertainment Expo was canceled. Miyamoto stated. So we decided not to reveal the controller and instead we displayed just the console." Nintendo president Satoru Iwata unveiled and demonstrated the Wii Remote at the September Tokyo Game Show. The Nintendo DS is said to have influenced the Wii's design. Designer Ken'ichiro Ashida noted, "We had the DS on our minds as we worked on the Wii. We thought about copying the DS's touch-panel interface and came up with a prototype." The idea was rejected because of the notion that the two gaming systems would be identical.
Miyamoto stated, " if the DS had flopped, we might have taken the Wii back to the drawing board." In June 2011 Nintendo unveiled the prototype of its successor to the Wii, to be known as the Wii U. The console was known by the code name "Revolution" from May 11, 2004 when its codename was announced at Nintendo's 2004 pre-Electronics Entertainment Expo press conference in Los Angeles, California until April 27, 2006 before E3. Before the Wii's codename was announced, the media referred to the console as "GCNext" or Gamecube Next and "N5" or Nintendo's fifth major home console. Nintendo's spelling of "Wii" is intended to resemble two people standing side-by-side and to represent the Wii Remote and Nunchuk. One reason the company has given for this name choice since the announcement is: Some video game developers and members of the press stated that they preferred "Revolution" over "Wii". Forbes expressed a fear "that the name would convey a continued sense of'kidiness' to the console." The BBC reported the day after the name was announced that "a long list of puerile jokes, based on the name," had appeared on the Internet.
Nintendo of America's Vice President of Corporate Affairs Perrin Kaplan defended the choice of "Wii" over "Revolution" and responded to critics of the name, stating "Live with it, sleep with it, eat with it, move along with it and they'll arrive at the same place." Nintendo of America's president Reggie Fils-Aime acknowledged the initial reaction and further explained the change: The Nintendo Style Guide refers to the console as "simply Wii, not Nintendo Wii", making it the first home console Nintendo has marketed outside Japan without the company name in its trademark. The Wii's successor, the Wii U, was marketed without Nintendo in its name, although its successor, the Nintendo Switch, brought back the Nintendo name in marketing. On September 14, 2006 Nintendo announced release information for J
File sharing is the practice of distributing or providing access to digital media, such as computer programs, documents or electronic books. File sharing may be achieved in a number of ways. Common methods of storage and dispersion include manual sharing utilizing removable media, centralized servers on computer networks, World Wide Web-based hyperlinked documents, the use of distributed peer-to-peer networking. Peer-to-peer file sharing is based on the peer-to-peer application architecture. Shared files on the computers of other users are indexed on directory servers. P2P technology was used by popular services like Limewire; the most popular protocol for P2P sharing is BitTorrent. Cloud-based file syncing and sharing services implement automated file transfers by updating files from a dedicated sharing directory on each user's networked devices. Files placed in this folder are accessible through a website and mobile app, can be shared with other users for viewing or collaboration; such services have become popular via consumer-oriented file hosting services such as Dropbox and Google Drive.
Rsync is a more traditional program released in 1996 which synchronizes files on a direct machine-to-machine basis. Data synchronization in general can use other approaches to share files, such as distributed filesystems, version control, or mirrors. Files were first exchanged on removable media. Computers were able to access remote files using filesystem mounting, bulletin board systems, FTP servers. Internet Relay Chat and Hotline enabled users to communicate remotely through chat and to exchange files; the mp3 encoding, standardized in 1991 and reduced the size of audio files, grew to widespread use in the late 1990s. In 1998, MP3.com and Audiogalaxy were established, the Digital Millennium Copyright Act was unanimously passed, the first mp3 player devices were launched. In June 1999, Napster was released as an unstructured centralized peer-to-peer system, requiring a central server for indexing and peer discovery, it is credited as being the first peer-to-peer file sharing system. Gnutella, eDonkey2000, Freenet were released in 2000, as MP3.com and Napster were facing litigation.
Gnutella, released in March, was the first decentralized file sharing network. In the gnutella network, all connecting software was considered equal, therefore the network had no central point of failure. In July, Freenet became the first anonymity network. In September the eDonkey2000 client and server software was released. In 2001, Kazaa and Poisoned for the Mac was released, its FastTrack network was distributed, though unlike gnutella, it assigned more traffic to'supernodes' to increase routing efficiency. The network was proprietary and encrypted, the Kazaa team made substantial efforts to keep other clients such as Morpheus off of the FastTrack network. In July 2001, Napster was sued by several recording companies and lost in A&M Records, Inc. v. Napster, Inc.. In the case of Napster, it has been ruled that an online service provider could not use the "transitory network transmission" safe harbor in the DMCA if they had control of the network with a server. Shortly after its loss in court, Napster was shut down to comply with a court order.
This drove users to other P2P applications and file sharing continued its growth. The Audiogalaxy Satellite client grew in popularity, the LimeWire client and BitTorrent protocol were released; until its decline in 2004, Kazaa was the most popular file sharing program despite bundled malware and legal battles in the Netherlands and the United States. In 2002, a Tokyo district court ruling shut down File Rogue, the Recording Industry Association of America filed a lawsuit that shut down Audiogalaxy. From 2002 through 2003, a number of BitTorrent services were established, including Suprnova.org, isoHunt, TorrentSpy, The Pirate Bay. In 2002, the RIAA was filing lawsuits against Kazaa users; as a result of such lawsuits, many universities added file sharing regulations in their school administrative codes. With the shutdown of eDonkey in 2005, eMule became the dominant client of the eDonkey network. In 2006, police raids took down the Razorback2 eDonkey server and temporarily took down The Pirate Bay.“The File Sharing Act was launched by Chairman Towns in 2009, this act prohibited the use of applications that allowed individuals to share federal information amongst one another.
On the other hand, only specific file sharing application were made available to federal computers”. In 2009, the Pirate Bay trial ended in a guilty verdict for the primary founders of the tracker; the decision was appealed, leading to a second guilty verdict in November 2010. In October 2010, Limewire was forced to shut down following a court order in Arista Records LLC v. Lime Group LLC but the gnutella network remains active through open source clients like Frostwire and gtk-gnutella. Furthermore, multi-protocol file sharing software such as MLDonkey and Shareaza adapted in order to support all the major file sharing protocols, so users no longer had to install and configure multiple file sharing programs. On January 19, 2012, the United States Department of Justice shut down the popular domain of Megaupload; the file sharing site has claimed to have over 50,000,000 people a day. Kim Dotcom was arrested with three associates in New Zealand on January 20, 2012 and is awaiting extradition; the case involving the downfall of the world's largest and most popular file sharing site was not well received, with hac
Ransomware is a type of malicious software from cryptovirology that threatens to publish the victim's data or perpetually block access to it unless a ransom is paid. While some simple ransomware may lock the system in a way, not difficult for a knowledgeable person to reverse, more advanced malware uses a technique called cryptoviral extortion, in which it encrypts the victim's files, making them inaccessible, demands a ransom payment to decrypt them. In a properly implemented cryptoviral extortion attack, recovering the files without the decryption key is an intractable problem – and difficult to trace digital currencies such as Ukash and cryptocurrency are used for the ransoms, making tracing and prosecuting the perpetrators difficult. Ransomware attacks are carried out using a Trojan, disguised as a legitimate file that the user is tricked into downloading or opening when it arrives as an email attachment. However, one high-profile example, the "WannaCry worm", traveled automatically between computers without user interaction.
Starting from around 2012 the use of ransomware scams has grown internationally. There were 181.5 million ransomware attacks in the first six months of 2018. This marks a 229% increase over this same time frame in 2017. In June 2013, vendor McAfee released data showing that it had collected more than double the number of samples of ransomware that quarter than it had in the same quarter of the previous year. CryptoLocker was successful, procuring an estimated US $3 million before it was taken down by authorities, CryptoWall was estimated by the US Federal Bureau of Investigation to have accrued over US $18m by June 2015; the concept of file encrypting ransomware was invented and implemented by Young and Yung at Columbia University and was presented at the 1996 IEEE Security & Privacy conference. It is called cryptoviral extortion and it was inspired by the fictional facehugger in the movie Alien. Cryptoviral extortion is the following three-round protocol carried out between the attacker and the victim.
The attacker places the corresponding public key in the malware. The malware is released. To carry out the cryptoviral extortion attack, the malware generates a random symmetric key and encrypts the victim's data with it, it uses the public key in the malware to encrypt the symmetric key. This is known as hybrid encryption and it results in a small asymmetric ciphertext as well as the symmetric ciphertext of the victim's data, it zeroizes the original plaintext data to prevent recovery. It puts up a message to the user how to pay the ransom; the victim sends the asymmetric e-money to the attacker. The attacker receives the payment, deciphers the asymmetric ciphertext with the attacker's private key, sends the symmetric key to the victim; the victim deciphers the encrypted data with the needed symmetric key thereby completing the cryptovirology attack. The symmetric key will not assist other victims. At no point is the attacker's private key exposed to victims and the victim need only send a small ciphertext to the attacker.
Ransomware attacks are carried out using a Trojan, entering a system through, for example, a malicious attachment, embedded link in a Phishing email, or a vulnerability in a network service. The program runs a payload, which locks the system in some fashion, or claims to lock the system but does not. Payloads may display a fake warning purportedly by an entity such as a law enforcement agency, falsely claiming that the system has been used for illegal activities, contains content such as pornography and "pirated" media; some payloads consist of an application designed to lock or restrict the system until payment is made by setting the Windows Shell to itself, or modifying the master boot record and/or partition table to prevent the operating system from booting until it is repaired. The most sophisticated payloads encrypt files, with many using strong encryption to encrypt the victim's files in such a way that only the malware author has the needed decryption key. Payment is always the goal, the victim is coerced into paying for the ransomware to be removed—which may or may not occur—either by supplying a program that can decrypt the files, or by sending an unlock code that undoes the payload's changes.
A key element in making ransomware work for the attacker is a convenient payment system, hard to trace. A range of such payment methods have been used, including wire transfers, premium-rate text messages, pre-paid voucher services such as paysafecard, the digital currency bitcoin. A 2016 survey commissioned by Citrix claimed that larger businesses are holding bitcoin as contingency plans; the first known malware extortion attack, the "AIDS Trojan" written by Joseph Popp in 1989, had a design failure so severe it was not necessary to pay the extortionist at all. Its payload hid the files on the hard drive and encrypted only their names, displayed a message claiming that the user's license to use a certain piece of software had expired; the user was asked to pay US$189 to "PC Cyborg Corporation" in order to obtain a repair tool though the decryption key could be extracted from the code of the Trojan. The Trojan was known as "PC Cyborg". Popp was declared mentally unfit to stand trial for his actions, but he promised to donate the profits from the malware to fund AIDS research.
The idea of abusing anonymous cash systems to safely collect ransom from human kidnapping was introduced in 1992 by Sebastiaan von Solms and David Naccache. This electronic money collec
Textfiles.com is a website dedicated to preserving the digital documents that contain the history of the bulletin board system world and various subcultures, thus providing "a glimpse into the history of writers and artists bound by the 128 characters that the American Standard Code for Information Interchange allowed them". The site categorizes and stores thousands of text files from the 1980s, but contains some older files and some that were created well into the 1990s. A broad range of topics is presented, including anarchy, carding, drugs, ezines. Freemasonry, hacking, politics, sex and UFOs; the site is run by Jason Scott. The site went online in 1998, as of 2005 had collected 58,227 files; as of 2017 the site was averaging 350,000-450,000 unique visitors per month. Most of the textfiles.com projects are "completionist" in outlook, attempting to gather as much information as possible within the decided scope. The site houses a number of sub-projects with their own hostnames. Artscene.textfiles.com has a repository of computer art including crack intros, ANSI and ASCII art and other related documents.
Archive Team BBS: The Documentary Internet Archive Phile Official website Archive of Short Talk Bulletin
A floppy disk known as a floppy, diskette, or disk, is a type of disk storage composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic enclosure lined with fabric that removes dust particles. Floppy disks are written by a floppy disk drive. Floppy disks as 8-inch media and in 5 1⁄4-inch and 3 1⁄2 inch sizes, were a ubiquitous form of data storage and exchange from the mid-1970s into the first years of the 21st century. By 2006 computers were manufactured with installed floppy disk drives; these formats are handled by older equipment. The prevalence of floppy disks in late-twentieth century culture was such that many electronic and software programs still use the floppy disks as save icons. While floppy disk drives still have some limited uses with legacy industrial computer equipment, they have been superseded by data storage methods with much greater capacity, such as USB flash drives, flash storage cards, portable external hard disk drives, optical discs, cloud storage and storage available through computer networks.
The first commercial floppy disks, developed in the late 1960s, were 8 inches in diameter. These disks and associated drives were produced and improved upon by IBM and other companies such as Memorex, Shugart Associates, Burroughs Corporation; the term "floppy disk" appeared in print as early as 1970, although IBM announced its first media as the "Type 1 Diskette" in 1973, the industry continued to use the terms "floppy disk" or "floppy". In 1976, Shugart Associates introduced the 5 1⁄4-inch FDD. By 1978 there were more than 10 manufacturers producing such FDDs. There were competing floppy disk formats, with hard- and soft-sector versions and encoding schemes such as FM, MFM, M2FM and GCR; the 5 1⁄4-inch format displaced the 8-inch one for most applications, the hard-sectored disk format disappeared. The most common capacity of the 5 1⁄4-inch format in DOS-based PCs was 360 KB, for the DSDD format using MFM encoding. In 1984 IBM introduced with its PC-AT model the 1.2 MB dual-sided 5 1⁄4-inch floppy disk, but it never became popular.
IBM started using the 720 KB double-density 3 1⁄2-inch microfloppy disk on its Convertible laptop computer in 1986 and the 1.44 MB high-density version with the PS/2 line in 1987. These disk drives could be added to older PC models. In 1988 IBM introduced a drive for 2.88 MB "DSED" diskettes in its top-of-the-line PS/2 models, but this was a commercial failure. Throughout the early 1980s, limitations of the 5 1⁄4-inch format became clear. Designed to be more practical than the 8-inch format, it was itself too large. A number of solutions were developed, with drives at 2-, 2 1⁄2-, 3-, 3 1⁄4-, 3 1⁄2- and 4-inches offered by various companies, they all shared a number of advantages over the old format, including a rigid case with a sliding metal shutter over the head slot, which helped protect the delicate magnetic medium from dust and damage, a sliding write protection tab, far more convenient than the adhesive tabs used with earlier disks. The large market share of the well-established 5 1⁄4-inch format made it difficult for these diverse mutually-incompatible new formats to gain significant market share.
A variant on the Sony design, introduced in 1982 by a large number of manufacturers, was rapidly adopted. The term floppy disk persisted though style floppy disks have a rigid case around an internal floppy disk. By the end of the 1980s, 5 1⁄4-inch disks had been superseded by 3 1⁄2-inch disks. During this time, PCs came equipped with drives of both sizes. By the mid-1990s, 5 1⁄4-inch drives had disappeared, as the 3 1⁄2-inch disk became the predominant floppy disk; the advantages of the 3 1⁄2-inch disk were its higher capacity, its smaller size, its rigid case which provided better protection from dirt and other environmental risks. If a person touches the exposed disk surface of a 5 1⁄4-inch disk through the drive hole, fingerprints may foul the disk—and the disk drive head if the disk is subsequently loaded into a drive—and it is easily possible to damage a disk of this type by folding or creasing it rendering it at least unreadable; however due to its simpler construction the 5 1⁄4-inch disk unit price was lower throughout its history in the range of a third to a half that of a 3 1⁄2-inch disk.
Floppy disks became commonplace during the 1980s and 1990s in their use with personal computers to distribute software, transfer data, create backups. Before hard disks became affordable to the general population, floppy disks were used to store a computer's operating system. Most home computers from that period have an elementary OS and BASIC stored in ROM, with the option of loading a more advanced operating system from a floppy disk. By the early 1990s, the increasing software size meant large packages like Windows or Adobe Photoshop required a dozen disks or more. In 1996, there were an estimated five billion standard floppy disks in use. Distribution of larger packages was replaced by CD-ROMs, DVDs and online distribution. An
Color Graphics Adapter
The Color Graphics Adapter also called the Color/Graphics Adapter or IBM Color/Graphics Monitor Adapter, introduced in 1981, was IBM's first graphics card and first color display card for the IBM PC. For this reason, it became that computer's first color computer display standard; the standard IBM CGA graphics card was equipped with 16 kilobytes of video memory and could be connected either to a dedicated direct-drive CRT monitor using a 4-bit digital RGBI interface, such as the IBM 5153 color display, or to an NTSC-compatible television or composite video monitor via an RCA connector. The RCA connector provided only baseband video, so to connect the CGA card to a standard television set required a separate RF modulator unless the TV had an RCA jack though with the former combined with an amplifier sometimes was more practical since one could hook up an antenna to the amplifier and get wireless video. Built around the Motorola MC6845 display controller, the CGA card featured several graphics and text modes.
The highest display resolution of any mode was 640×200, the highest color depth supported was 4-bit. CGA supports: 320×200 in 4 colors from a 16 color hardware palette. Pixel aspect ratio of 1:1.2. 640×200 in 2 colors. Pixel aspect ratio of 1:2.4 Text modes: 40×25 with 8×8 pixel font 80×25 with 8×8 pixel font Extended graphics modes: 160×100 16 color mode Artifact colors using a NTSC monitor IBM intended that CGA be compatible with a home television set. The 40×25 text and 320×200 graphics modes are usable with a television, the 80×25 text and 640×200 graphics modes are intended for a monitor. Despite varying bit depths among the CGA graphics modes, CGA processes colors in its palette in four bits, yielding 24 = 16 different colors; the four color bits are arranged according to the RGBI color model: the lower three bits represent red and blue color components. In graphics modes, colors are set per-pixel; these four bits are passed on unmodified to the DE-9 connector at the back of the card, leaving all color processing to the RGBI monitor connected to it.
With respect to the RGBI color model described above, the monitor would use the following formula to process the digital four-bit color number to analog voltages ranging from 0.0 to 1.0: red:= 2/3×/4 + 1/3×/8 green:= 2/3×/2 + 1/3×/8 blue:= 2/3×/1 + 1/3×/8 Color 6 is treated differently. For the composite output, these four-bit color numbers are encoded by the CGA's onboard hardware into an NTSC-compatible signal fed to the card's RCA output jack. For cost reasons, this is not done using an RGB-to-YIQ converter as called for by the NTSC standard, but by a series of flip-flops and delay lines; the hues seen are lacking in purity. The relative luminances of the colors produced by the composite color-generating circuit differ between CGA revisions: they are identical for colors 1-6 and 9-14 with early CGAs produced until 1983, are different for CGAs due to the addition of additional resistors; as noted however, this method only works on NTSC television sets, PAL TVs do not display the colors as expected when connected to the composite output, as PAL's superior color separation prevents artifacting from occurring.
When the CGA was introduced in 1981, IBM did not offer an RGBI monitor. Instead, customers were supposed to use the RCA output with an RF modulator to connect the CGA to their television set; the IBM 5153 Personal Computer Color Display would not be introduced until March 1983. Resulting from the lack of available RGBI monitors in 1981 and 1982, many users would use simpler RGB monitors, reducing the number of available colors to eight, displaying both colors 6 and 14 as yellow; this is relevant insofar as if an application or game programmer used either one of these configurations, they will have expected color 6 to look dark yellow instead of brown. CGA offers four BIOS text modes: 40×25 characters in up to 16 colors; each character is a pattern of 8×8 dots. The effective screen resolution in this mode is 320×200 pixels, though individual pixels cannot be addressed independently; the choice of patterns for any location is thus limited to one of the 256 available characters, the patterns for which are stored in a ROM chip on the card itself.
The display font in text mode i