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Encyclopédie, ou dictionnaire raisonné des sciences, des arts et des métiers (English: Encyclopedia, or a Systematic Dictionary of the Sciences, Arts, and Crafts), better known as Encyclopédie, was a general encyclopedia published in France between 1751 and 1772, with later supplements, revised editions, and translations.
A 7 January 1989 match between Sutton United and Coventry City took place as part of the third round of the 1988–89 FA Cup association football competition. Coventry City were in the top tier of English league football, while Sutton United were in the fifth.
– in Europe (green & dark grey) – in the European Union (green) Capital and largest city Paris 48°51′N 2°21′E / 48.850°N 2.350°E / 48.850; 2.350 Official language and national language French [I] Nationality (2018) 93.0% French citizens 7.0% foreign nationals Religion (2019) 51% Christianity 40% No religion 5% Islam 3% Other 1% Undeclared Demonym(s) French Government ...
French français Pronunciation [fʁɑ̃sɛ] Region Originated in France, now worldwide especially France, Canada, Belgium, Switzerland, North Africa and West Africa (distribution maps below) Ethnicity French people Native speakers 76.8 million worldwide An estimated 274 million French speakers (L1 plus L2 ; 2014) Language family Indo-European Italic Romance Western Romance Gallo-Romance Oïl ...
- Technical Foundations
- File Format
- Imaging Model
- Additional Features
- See Also
A PDF file contains 7-bit ASCII characters, except for certain elements that may have binary content.The file starts with a header containing a magic number (as a readable string) and the version of the format, for example %PDF-1.7. The format is a subset of a COS ("Carousel" Object Structure) format. A COS tree file consists primarily of objects, of which there are nine types: 1. Boolean values, representing true or false 2. Real numbers 3. Integers 4. Strings, enclosed within parentheses ((...)). Strings may contain 8-bit characters. 5. Names, starting with a forward slash (/) 6. Arrays, ordered collections of objects enclosed within square brackets ([...]) 7. Dictionaries, collections of objects indexed by names enclosed within double angle brackets (<<...>>) 8. Streams, usually containing large amounts of optionally compressed binary data, preceded by a dictionary and enclosed between the stream and endstreamkeywords. 9. The nullobject Furthermore, there may be comments, introdu...
The basic design of how graphics are represented in PDF is very similar to that of PostScript, except for the use of transparency, which was added in PDF 1.4. PDF graphics use a device-independent Cartesian coordinate system to describe the surface of a page. A PDF page description can use a matrix to scale, rotate, or skew graphical elements. A key concept in PDF is that of the graphics state, which is a collection of graphical parameters that may be changed, saved, and restored by a page description. PDF has (as of version 2.0) 25 graphics state properties, of which some of the most important are: 1. The current transformation matrix(CTM), which determines the coordinate system 2. The clipping path 3. The color space 4. The alpha constant, which is a key component of transparency 5. Black point compensationcontrol (introduced in PDF 2.0)
Logical structure and accessibility
A "tagged" PDF (see clause 14.8 in ISO 32000) includes document structure and semantics information to enable reliable text extraction and accessibility. Technically speaking, tagged PDF is a stylized use of the format that builds on the logical structure framework introduced in PDF 1.3. Tagged PDF defines a set of standard structure types and attributes that allow page content (text, graphics, and images) to be extracted and reused for other purposes. Tagged PDF is not required in situations...
Optional Content Groups
With the introduction of PDF version, 1.5 (2003) came the concept of Layers. Layers, or as they are more formally known Optional Content Groups (OCGs), refer to sections of content in a PDF document that can be selectively viewed or hidden by document authors or consumers. This capability is useful in CAD drawings, layered artwork, maps, multi-language documents, etc. Basically, it consists of an Optional Content Properties Dictionary added to the document root. This dictionary contains an ar...
Encryption and signatures
A PDF file may be encrypted, for security, in which case a password is needed to view or edit the contents. PDF 2.0 defines 256-bit AES encryption as standard for PDF 2.0 files. The PDF Reference also defines ways that third parties can define their own encryption systems for PDF. PDF files may be digitally signed, to provide secure authentication; complete details on implementing digital signatures in PDF is provided in ISO 32000-2. PDF files may also contain embedded DRMrestrictions that pr...
Anyone may create applications that can read and write PDF files without having to pay royalties to Adobe Systems; Adobe holds patents to PDF, but licenses them for royalty-freeuse in developing software complying with its PDF specification.
In November 2019, researchers from Ruhr University Bochum and Hackmanit GmbH published attacks on digitally signed PDFs .They showed how to change the visible content in a signed PDF without invalidating the signature in 21 of 22 desktop PDF viewers and 6 of 8 online validation services by abusing implementation flaws.On the same conference, they additionally showed how to exfiltrate the plaintext of encrypted content in PDFs.In 2021, they showed new so-called shadow attacks on PDFs that abuse the flexibilty of features provided in the specification.An overview of security issues in PDFs regarding denial of service, information disclosure, data manipulation, and Arbitrary code executionattacks was presented by Jens Müller. PDF attachments carrying viruses were first discovered in 2001. The virus, named OUTLOOK.PDFWorm or Peachy, uses Microsoft Outlookto send itself as an attached Adobe PDF file. It was activated with Adobe Acrobat, but not with Acrobat Reader. From time to time, new...
Viewers and editors
PDF viewers are generally provided free of charge, and many versions are available from a variety of sources. There are many software options for creating PDFs, including the PDF printing capabilities built into macOS, iOS, and most Linux distributions, LibreOffice, Microsoft Office 2007 (if updated to SP2) and later, WordPerfect 9, Scribus, numerous PDF print drivers for Microsoft Windows, the pdfTeX typesetting system, the DocBook PDF tools, applications developed around Ghostscript and Ado...
Raster image processors (RIPs) are used to convert PDF files into a raster format suitable for imaging onto paper and other media in printers, digital production presses and prepress in a process known as rasterisation. RIPs capable of processing PDF directly include the Adobe PDF Print Engine from Adobe Systems and Jaws and the Harlequin RIP from Global Graphics. In 1993 the Jaws raster image processor from Global Graphicsbecame the first shipping prepress RIP that interpreted PDF natively w...
Native display model
PDF was selected as the "native" metafile format for Mac OS X, replacing the PICT format of the earlier classic Mac OS. The imaging model of the Quartz graphics layer is based on the model common to Display PostScript and PDF, leading to the nickname Display PDF. The Preview application can display PDF files, as can version 2.0 and later of the Safari web browser. System-level support for PDF allows Mac OS X applications to create PDF documents automatically, provided they support the OS-stan...
The Open XML Paper Specification is a competing format used both as a page description language and as the native print spooler format for Microsoft Windows since Windows Vista.
PDF/A is an ISO-standardized version of the Portable Document Format (PDF) specialized for use in the archiving and long-term preservation of electronic documents.PDF/A differs from PDF by prohibiting features unsuitable for long-term archiving, such as font linking (as opposed to font embedding) and encryption.
Distinction (philosophy), the recognition of difference. Formal distinction. Distinction (law), a principle in international law governing the legal use of force in an armed conflict. Distinction (sociology), a social force that places different values on different individuals. Distinct (mathematics) Distinctive feature, a concept in linguistics.
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