Misplaced Pages

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47-428: Fixedsys fonts family contains fonts encoded in several Windows code pages , with multiple resolutions of the font for each code page. Fixedsys fonts of different code pages have different point sizes. The glyphs for the upper areas of each one appear to be drawn separately, not taken from a single master set, as there are visible differences in the appearance of various visually similar characters that are shared between

94-510: A data warehouse . In either case, the effect on business intelligence and operational reporting can be significant. A legacy system may include procedures or terminology which are no longer relevant in the current context, and may hinder or confuse understanding of the methods or technologies used. Organizations can have compelling reasons for keeping a legacy system, such as: Legacy systems are considered to be potentially problematic by some software engineers for several reasons. Where it

141-449: A graphical user interface on Windows systems. The term "ANSI" is a misnomer because these Windows code pages do not comply with any ANSI (American National Standards Institute) standard; code page 1252 was based on an early ANSI draft that became the international standard ISO 8859-1 , which adds a further 32 control codes and space for 96 printable characters. Among other differences, Windows code-pages allocate printable characters to

188-521: A `challenge` to current coders to create code that is "like other legacies in our lives—like the antiques, heirlooms, and stories that are cherished and lovingly passed down from one generation to the next. What if legacy code was something we took pride in?". The term legacy support is often used in conjunction with legacy systems. The term may refer to a feature of modern software. For example, Operating systems with "legacy support" can detect and use older hardware. The term may also be used to refer to

235-406: A business function; e.g. a software or hardware vendor that is supporting, or providing software maintenance , for older products. A "legacy" product may be a product that is no longer sold, has lost substantial market share, or is a version of a product that is not current. A legacy product may have some advantage over a modern product making it appealing for customers to keep it around. A product

282-840: A later version of a system, or requires a compatibility layer to do so. An example would be a classic Macintosh application which will not run natively on macOS , but runs inside the Classic environment , or a Win16 application running on Windows XP using the Windows on Windows feature in XP. An example of legacy hardware are legacy ports like PS/2 and VGA ports, and CPUs with older, incompatible instruction sets (with e.g. newer operating systems). Examples in legacy software include legacy file formats like .swf for Adobe Flash or .123 for Lotus 1-2-3 , and text files encoded with legacy character encodings like EBCDIC . The first use of

329-447: A system is out of date, a legacy system can continue to be used for a variety of reasons. It may simply be that the system still provides for the users' needs. In addition, the decision to keep an old system may be influenced by economic reasons such as return on investment challenges or vendor lock-in , the inherent challenges of change management , or a variety of other reasons other than functionality. Backward compatibility (such as

376-485: Is a codebase that is in some respect obsolete or supporting something obsolete. Legacy code may be written in programming languages, use frameworks and external libraries, or use architecture and patterns that are no longer considered modern, increasing the mental burden and ramp-up time for software engineers who work on the codebase. Legacy code may have zero or insufficient automated tests , making refactoring dangerous and likely to introduce bugs . Long-lived code

423-538: Is also used as an ANSI code page. These often differ from the IBM code pages of the same number: code pages 932, 949 and 950 only partly match the IBM code pages of the same number, while the number 936 was used by IBM for another Simplified Chinese encoding which is now deprecated and Windows-951, as part of a kludge , is unrelated to IBM-951. IBM equivalent code pages are given in the second column. Code pages 932, 936, 949 and 950/951 are used as both ANSI and OEM code pages on

470-526: Is also used as an OEM code page. The Windows-125x series includes nine of the ANSI code pages, and mostly covers scripts from Europe and West Asia with the addition of Vietnam . System encodings for Thai and for East Asian languages were numbered to match similar IBM code pages and are used as both ANSI and OEM code pages; these are covered in following sections. These are also ASCII-based. Most of these are included for use as OEM code pages; code page 874

517-463: Is an old method, technology, computer system , or application program , "of, relating to, or being a previous or outdated computer system", yet still in use. Often referencing a system as "legacy" means that it paved the way for the standards that would follow it. This can also imply that the system is out of date or in need of replacement. Legacy code is old computer source code that is no longer supported on standard hardware and environments, and

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564-438: Is impossible to replace legacy systems through the practice of application retirement , it is still possible to enhance (or "re-face") them. Most development often goes into adding new interfaces to a legacy system. The most prominent technique is to provide a Web-based interface to a terminal-based mainframe application. This may reduce staff productivity due to slower response times and slower mouse-based operator actions, yet it

611-537: Is in contrast to VISCII , which replaces some of the C0 (i.e. ASCII) control codes. Early computer systems had limited storage and restricted the number of bits available to encode a character . Although earlier proprietary encodings had fewer, the American Standard Code for Information Interchange (ASCII) settled on seven bits: this was sufficient to encode a 96 member subset of the characters used in

658-468: Is monospaced. A smaller CGA version of this font also exists, with some characters bearing a resemblance to the IBM 8x8 CGA font. The EGA version is nearly identical to the CGA version, only in differing in a small number of characters. According to a string embedded in the .FON file (which is viewable with a hex editor or with a typeface editor such as Fony), this font was designed in 1984 by Bitstream Inc., but

705-410: Is often seen as an "upgrade", because the interface style is familiar to unskilled users and is easy for them to use. John McCormick discusses such strategies that involve middleware . Printing improvements are problematic because legacy software systems often add no formatting instructions, or they use protocols that are not usable in modern PC/Windows printers. A print server can be used to intercept

752-567: Is only truly "obsolete" if it has an advantage to nobody —if no person making a rational decision would choose to acquire it new. The term "legacy mode" often refers specifically to backward compatibility . A software product that is capable of performing as though it were a previous version of itself, is said to be "running in legacy mode". This kind of feature is common in operating systems and internet browsers, where many applications depend on these underlying components. The computer mainframe era saw many applications running in legacy mode. In

799-432: Is susceptible to software rot , where changes to the runtime environment, or surrounding software or hardware may require maintenance or emulation of some kind to keep working. Legacy code may be present to support legacy hardware, a separate legacy system, or a legacy customer using an old feature or software version. While the term usually refers to source code, it can also apply to executable code that no longer runs on

846-540: Is the American National Standards Institute .) Code pages in both of these groups are extended ASCII code pages. Additional code pages are supported by standard Windows conversion routines, but not used as either type of system code page. ANSI code pages (officially called "Windows code pages" after Microsoft accepted the former term being a misnomer ) are used for native non-Unicode (say, byte oriented ) applications using

893-447: Is treated as a synonym for " GBK ". Windows code page 932 is instead labelled as "Windows-31J". ANSI Windows code pages, and especially the code page 1252 , were so called since they were purportedly based on drafts submitted or intended for ANSI. However, ANSI and ISO have not standardized any of these code pages. Instead they are either: Microsoft assigned about twelve of the typography and business characters (including notably,

940-918: The Basic Multilingual Plane (BMP) using 16 bits but the remaining Unicode (e.g. emojis ) is encoded with a 32-bit (four byte) code – while the rest of the industry ( Unix-like systems and the web), and now Microsoft chose UTF-8 (which uses one byte for the 7-bit ASCII character set, two or three bytes for other characters in the BMP, and four bytes for the remainder). The following Windows code pages exist: These nine code pages are all extended ASCII 8-bit SBCS encodings, and were designed by Microsoft for use as ANSI codepages on Windows. They are commonly known by their IANA-registered names as windows-<number> , but are also sometimes called cp<number> , "cp" for "code page". They are all used as ANSI code pages; Windows-1258

987-570: The euro sign , €) in CP1252 to the code points 0x80–0x9F that, in ISO ;8859, are assigned to C1 control codes . These assignments are also present in many other ANSI/Windows code pages at the same code-points. Windows did not use the C1 control codes, so this decision had no direct effect on Windows users. However, if included in a file transferred to a standards-compliant platform like Unix or MacOS,

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1034-540: The 1980s and 1990s. Windows code pages were gradually superseded when Unicode was implemented in Windows , although they are still supported both within Windows and other platforms, and still apply when Alt code shortcuts are used. Current Windows versions support Unicode , new Windows applications should use Unicode (UTF-8) and not 8-bit character encodings. There are two groups of system code pages in Windows systems: OEM and Windows-native ("ANSI") code pages. (ANSI

1081-666: The Americas, southern and south-east Asia, the Middle East and Europe, a character needs just one byte but two or more bytes are needed for the ideographic sets used in the rest of the world. The code-page model was unable to handle this challenge. Since the late 1990s, software and systems have adopted Unicode as their preferred character encoding format: Unicode is designed to handle millions of characters. All current Microsoft products and application program interfaces use Unicode internally, but some applications continue to use

1128-471: The Space Shuttle program. Thus any new system that started the certification process becomes a de facto legacy system by the time it is approved for flight. Additionally, the entire Space Shuttle system, including ground and launch vehicle assets, was designed to work together as a closed system. Since the specifications did not change, all of the certified systems and components performed well in

1175-540: The US. As eight-bit bytes came to predominate, Microsoft (and others) expanded the repertoire to 224, to handle a variety of other uses such a box-drawing symbols. The need to provide precomposed characters for the Western European and South American markets required a different character set: Microsoft established the principle of code pages, one for each alphabet. For the segmental scripts used in most of Africa,

1222-494: The Windows encodings (although most are similar). While code page 1258 is also used as an OEM code page, it is original to Microsoft rather than an extension to an existing encoding. IBM have assigned their own, different numbers for Microsoft's variants, these are given for reference in the lists below where applicable. All of the 125x Windows code pages, as well as 874 and 936, are labelled by Internet Assigned Numbers Authority (IANA) as "Windows- number ", although "Windows-936"

1269-444: The ability of newer systems to handle legacy file formats and character encodings ) is a goal that software developers often include in their work. Even if a legacy system is no longer used, it may continue to impact the organization due to its historical role. Historic data may not have been converted into the new system format and may exist within the new system with the use of a customized schema crosswalk , or may exist only in

1316-437: The capability to use and maintain the system are crucial. Otherwise the system will become less and less understandable and maintainable. According to Hein, verification, validation, testing, and operational history increases the confidence in a system's reliability and quality. However, accumulating this history is often expensive. NASA's now retired Space Shuttle program used a large amount of 1970s-era technology. Replacement

1363-755: The changes can be incorporated quickly and easily in the ABP software. Model-driven reverse and forward engineering approaches can be also used for the improvement of legacy software. Andreas M. Hein researched the use of legacy systems in space exploration at the Technical University of Munich. According to Hein, legacy systems are attractive for reuse if an organization has the capabilities for verification, validation, testing, and operational history. These capabilities must be integrated into various software life cycle phases such as development, implementation, usage, or maintenance. For software systems,

1410-753: The code pages. Though Fixedsys is a sans-serif font, it is vaguely similar in appearance to the hardware text mode font of most IBM-compatible PCs , though not as similar as certain sizes of Terminal fonts seen in Windows. In Windows 95 , 98 , and Windows Me , Fixedsys remains as the default font for Notepad. This font was superseded by Lucida Console in Notepad for later versions of Windows. In Windows 95 , this default font cannot be changed. Fixedsys of other code pages can be selected by specifying script settings in font selection dialogue, but not font of all code pages can be chosen. Due to its clean style and easy readability, it has enjoyed some popularity with

1457-911: The cost of replacing business logic is about five times that of reuse, even discounting the risk of system failures and security breaches. Ideally, businesses would never have to rewrite most core business logic: debits = credits is a perennial requirement. The IT industry is responding with "legacy modernization" and "legacy transformation": refurbishing existing business logic with new user interfaces, sometimes using screen scraping and service-enabled access through web services . These techniques allow organizations to understand their existing code assets (using discovery tools), provide new user and application interfaces to existing code, improve workflow, contain costs, minimize risk, and enjoy classic qualities of service (near 100% uptime, security, scalability, etc.). This trend also invites reflection on what makes legacy systems so durable. Technologists are relearning

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1504-403: The data and translate it to a more modern code. Rich Text Format (RTF) or PostScript documents may be created in the legacy application and then interpreted at a PC before being printed. Biometric security measures are difficult to implement on legacy systems. A workable solution is to use a Telnet or HTTP proxy server to sit between users and the mainframe to implement secure access to

1551-576: The default encoding of the computer's 'locale' when reading and writing text data to files or standard output. Therefore, files may still be encountered that are legible and intelligible in one part of the world but unintelligible mojibake in another. Microsoft adopted a Unicode encoding (first the now-obsolete UCS-2 , which was then Unicode's only encoding), i.e. UTF-16 for all its operating systems from Windows NT onwards, but additionally supports UTF-8 (aka CP_UTF8 ) since Windows 10 version 1803 . UTF-16 uniquely encodes all Unicode characters in

1598-649: The high resolution 8514/a version (used in modern versions of Windows operating system as the high DPI variant, which is larger and looks different from the VGA version) was designed in 1987 by Microsoft Corporation. The following is the lorem ipsum as it appears here written in Fixedsys. Windows code page Windows code pages are sets of characters or code pages (known as character encodings in other operating systems) used in Microsoft Windows from

1645-427: The importance of sound architecture from the start, to avoid costly and risky rewrites. The most common legacy systems tend to be those which embraced well-known IT architectural principles, with careful planning and strict methodology during implementation. Poorly designed systems often don't last, both because they wear out and because their inherent faults invite replacement. Thus, many organizations are rediscovering

1692-579: The information was invisible and potentially disruptive. The OEM code pages ( original equipment manufacturer ) are used by Win32 console applications, and by virtual DOS , and can be considered a holdover from DOS and the original IBM PC architecture. A separate suite of code pages was implemented not only due to compatibility, but also because the fonts of VGA (and descendant) hardware suggest encoding of line-drawing characters to be compatible with code page 437 . Most OEM code pages share many code points, particularly for non-letter characters, with

1739-411: The legacy application. The change being undertaken in some organizations is to switch to automated business process (ABP) software which generates complete systems. These systems can then interface to the organizations' legacy systems and use them as data repositories . This approach can provide a number of significant benefits: the users are insulated from the inefficiencies of their legacy systems, and

1786-404: The locales in question. A few further multiple-byte code pages are supported for decoding or encoding using operating system libraries, but not used as either sort of system encoding in any locale. Microsoft strongly recommends using Unicode in modern applications, but many applications or data files still depend on the legacy code pages. Legacy system In computing , a legacy system

1833-431: The modern business computing environment, n-tier , or 3-tier architectures are more difficult to place into legacy mode as they include many components making up a single system. Virtualization technology is a recent innovation allowing legacy systems to continue to operate on modern hardware by running older operating systems and browsers on a software system that emulates legacy hardware. Programmers have borrowed

1880-493: The programming community, even giving rise to an imitation font — Fixedsys Excelsior — which, based on the original Fixedsys typeface, also includes a large number of Unicode script ranges. There is a certain amount of similarity between Fixedsys and Chicago , the default system typeface on the Apple Macintosh between 1984 and 1997. The key difference is that Chicago is a proportional typeface while Fixedsys

1927-557: The roles for which they were designed. Even before the Shuttle was scheduled to be retired in 2010, NASA found it advantageous to keep using many pieces of 1970s technology rather than to upgrade those systems and recertify the new components. Some in the software engineering prefer to describe "legacy code" without the connotation of being obsolete. Among the most prevalent neutral conceptions are source code inherited from someone else and source code inherited from an older version of

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1974-464: The second (non-ASCII) half of CP437. A typical OEM code page, in its second half, does not resemble any ANSI/Windows code page even roughly. Nevertheless, two single-byte, fixed-width code pages (874 for Thai and 1258 for Vietnamese ) and four multibyte CJK code pages ( 932 , 936 , 949 , 950 ) are used as both OEM and ANSI code pages. Code page 1258 uses combining diacritics , as Vietnamese requires more than 128 letter-diacritic combinations. This

2021-456: The software . Eli Lopian, CEO of Typemock, has defined it as "code that developers are afraid to change". Michael Feathers introduced a definition of legacy code as code without tests , which reflects the perspective of legacy code being difficult to work with in part due to a lack of automated regression tests . He also defined characterization tests to start putting legacy code under test. Ginny Hendry characterized creation of code as

2068-461: The supplementary control code space, making them at best illegible to standards-compliant operating systems.) Most legacy "ANSI" code pages have code page numbers in the pattern 125x. However, 874 (Thai) and the East Asian multi-byte "ANSI" code pages ( 932 , 936 , 949 , 950 ), all of which are also used as OEM code pages, are numbered to match IBM encodings, none of which are identical to

2115-482: The term brownfield from the construction industry, where previously developed land (often polluted and abandoned) is described as brownfield . There is an alternate favorable opinion—growing since the end of the Dotcom bubble in 1999—that legacy systems are simply computer systems in working use: " Legacy code " often differs from its suggested alternative by actually working and scaling. IT analysts estimate that

2162-412: The term legacy to describe computer systems probably occurred in the 1960s. By the 1980s it was commonly used to refer to existing computer systems to distinguish them from the design and implementation of new systems. Legacy was often heard during a conversion process, for example, when moving data from the legacy system to a new database. While this term may indicate that some engineers may feel that

2209-407: Was cost-prohibitive because of the expensive requirement for flight certification. The original hardware completed the expensive integration and certification requirement for flight, but any new equipment would have had to go through that entire process again. This long and detailed process required extensive tests of the new components in their new configurations before a single unit could be used in

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