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`WHATSAPP INC.'S EXHIBIT NO. 1020
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`001
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`

`
`Qq 76.15 .D526 2004
`computing 5th ed.
`pictionary of
`
`i
`
`_
`
`~ t~—____---
`
`QA 76.15 .D526 2004
`
`Dictionary of computing, 5th ed.
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`to m
`9
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`306
`
`~
`
`307
`
`~
`
`simple Boolean functions and for flipflops,
`as shown in the diagram.
`login (logon) The process by which a user
`identifies herself or himself to a system.
`The terms aze also used as verbs: login,
`log on, or sign on. A system with many reg
`istered users will require each user to log
`in, and to produce some form of *authen-
`tication (such as a password) before allow
`ing the user access to system resources.
`The login activity will also open an *ac-
`countingfile for the session.
`logistic function A ratio of sums of ex-
`ponentials widely used in statistical analy-
`sis. The logistic function lies in the range
`(0,1), and iu inverse, lmown as the logit of
`a proportion, is the logarithm of the odds-
`ratio (see onns).
`logit See Locisxic Fuxcriox.
`LOGO A programming language devel-
`oped for use in teaching young children.
`LOGO is a simple but powerful language:
`it incorporates the concept of *pro-
`cedures, and helps children to think algo-
`rithmically. The original version of LOGO
`incorporated *turtle graphics.
`logoff (logout) The process by which a
`user terminates a session. The terms are
`also used as verbs: log off, log out, or sign
`off. By logging off, the user ensures that all
`the system resources that have been used
`during the session aze accounted for, and
`any temporary files created during the ses-
`sion are deleted.
`logon 1. (or log on) See Locix.
`2. A unit of information, equal to the
`product of one unit of *bandwidth by one
`unit of time, in Denis Gabor's physical
`theory of communication. In contrast,
`Shannon's mathematical theory of com-
`munication uses the concept of *entropy.
`logout (or log out) See LocoFF.
`long filename A file name that may
`have a large number ofcharacters, includ-
`ing spaces, and use upper- and lowercase
`letters. Long filenames are now supported
`on most personal~omputer operating sys-
`tems. In earlier systems, the 8.3 system was
`common -files had a name of up to eight
`characters maximum, followed by a dot,
`followed by a file extension of up to three
`characters. For example, in this dictionary
`
`the file containing this entry is called
`"OUPCOMOL.XML". On along-filename sys-
`tem, it could be called "Oxford University
`Press Computing Dictionary letter L.XML
`file".
`longitudinal redundancy check (LRC)
`$C2 CYCLIC REDUNDANCY CHECK
`lookahead Short for carry lookahead.
`lookahead unit A unit forming part of
`an instruction unit pipeline in computers
`such as *Stretch.
`lookup table See xaar.~ LooxuP.
`loop 1. A sequence of instructions that is
`repeated until a prescribed condition,
`such as agreement with a data element or
`completion of a count, is satisfied. See also
`DO LOOP.
`2. A configuration of a *local azea network
`that consists of nodes connected serially
`in a ring topology. See iuxc x~rwoxx.
`3. (local loop) The (twisted pair) connec-
`tion from a switching exchange to the
`subscriber terminal.
`loop invariant See ixvnxinrrr.
`lossless coding Coding in which no *in-
`formation whauoever is lost during the
`*encoding (or *decoding) process. Gener
`ally, *encryption and *decryption aze loss-
`less, as is *channel coding. Strictly, *data
`compaction is lossless, while *data com-
`pression is not, but the latter term is often
`used for the former. The decoding of (i.e.
`recovery from) compression and com
`paction are lossless. But the decoding of a
`signal received from a *channel is usually
`lossy (strictly not lossless) by design, since
`the *noise at least must be lost: the mes-
`sage entering the channel will usually
`have been prepared so as to permit this
`loss by the use of an *errorcorrecting
`code.
`lossless compression Any method of
`*compression that allows the original data
`to be recovered from the compressed data.
`$22 ALSO LOSSLESS CODING.
`lossy coding Any form of coding in
`which *information is or maybe lost. See
`LOSSLESS CODING.
`lossy compression *Compression of
`data that approximates the original data
`so that it is not possible for it to be recov-
`
`ered identically. However a good approxi-
`mation should always be possible. See also
`LOSSLESS CODING.
`Lotus 1-2-3 TrademarkA *spreadsheet
`program originally from Lotus Develop-
`ment Corp. (now part of IBMj for personal
`computers. It also provides simple statisti-
`cal and database facilities and graph draw-
`ing of pie charts, bar charts, and line
`graphs.
`lower bound 1. of a set S on which the
`*partial ordering < is defined. An element 1
`with the property that 1 < s for all s in S.
`Also 1 is a greatest lower bound if; for any
`other lower bound h, h < 1.
`Since numerical computing demands
`the truncation of infinite arithmetic to
`Snite arithmetic, the computation of
`greatest lower bounds of real numbers, in-
`deed of any limit, can only be achieved to
`a machine tolerance, usually defined to be
`machine precision: the smallest epsilon
`eps, such that
`1.0 + eps > 1.0
`in computer arithmetic. See also urrEx
`BOUND.
`2. of a matrix or vector. See AxxnY.
`low-level language A vaziety of pro-
`gra,,,,,,;,,g language in which the control
`and data structures directly reflect the un-
`derlying machine architecture.
`low-level scheduler (dispatcher) See
`SCHEDULER
`low-pass filter A *filtering device that
`pernuts only those components in the fre-
`quency domain whose frequencies lie
`below some critical value to pass through
`with little attenuation, all other compo-
`nents being highly attenuated. See also
`BAND-STOP FILTER, BAND-PASS FILTER, HIGH-
`PASS FILTER
`Ipm Abbrev for lines per minute, one of
`the terms used to describe the rate of out-
`put of line printers.
`LPT port The name of a parallel printer
`port on an IBM PC or compatible. There
`can be up to three of these ports, called
`LPTl, LPT2, and LPT3. They are *Centron-
`ics interfaces and while designed with
`printers in mind can be used for other de-
`vices such as tape backup systems or net-
`work connections.
`
`LR parsing
`
`LQ Abbrev. for letter quality. Printed output
`indistinguishable from that produced by a
`good electric typewriter. The term is nor
`orally applied to dot matrix printers. See
`11L50 NLQ
`LRC Abbrev for longitudinal redundacy
`check. See crcuc xanuxnnxcY cxacic
`LRM Abbrev for language reference man-
`ual. The reference manual for the *Ada
`language is commonly lmown as "the
`LRM"-
`LR parsing A *bottom-up parsing tech-
`nique, LR standing for Left-to-right Right-
`most derivation sequence. Oria Wally
`developed by D. E. Knuth, it is the most
`powerful left-to-right, no backtracking
`parsing method for *conteact-free gram-
`mars.
`An LR parser consists of a pushdown
`stack, a pazsing table, and a driving rou-
`tine. The driving routine is the same for
`all grammars. The stack is manipulated by
`the driving routine using the information
`contained in the top stack element and
`the next k symbols in the input stream
`(called the k lookahead); k is an integer ?0,
`but for most practical purposes k =1. T'he
`stack consists of a string
`soXos,X,...soXnsa.,
`where each X; is a symbol of the input
`grammar and each s; is called a state.
`The parsing table is indexed by pairs
`(s,a) where s is a state and a is the look-
`ahead. Each entry in the table has two
`parts: (a) an action, which maybe shift, re-
`duce p (for some producrion p), accept, or
`error, and (b) a state, called the goto state.
`When the action is shift, the next input
`symbol and goto state are pushed onto the
`stack (in that order). When the action is
`reduce p the top 21 elements of the stack
`will spell the right-hand side ofp but with
`goto states interspersed, where 1 is the
`length of this right-hand side. These 21 el-
`ements are. popped from the stack and re-
`placed by the left-hand side ofp and the
`new goto state. This operation corre-
`sponds to adding a new node to the *parse
`tree for the input string. The accept action
`is only encountered when the start sym-
`bol S is the only symbol on the stack (ie.
`the stack contains soSs, for some states so
`and s,) and the lookahead is the end-of-
`input symbol. It signifies that parsing has
`
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`
`systems software
`
`524
`
`systems software (system software)
`The totality of software required to pro-
`duce a system acceptable to end users. See
`QISO SYSTEMS PROGRAMMING.
`systems theory The study of *systems
`in themselves, usually to find characteris-
`tics common to all systems or to classes of
`systems. Systems theorists maybe most
`concerned with the development of
`theory for its own sake (most often called
`general systems theory), or they maybe more
`concerned with the applications of sys-
`tems ideas within particular disciplines or
`problem areas in order to solve problems
`that aze not amenable to traditional "re-
`ductionisY' approaches. Systems theory
`has been called the study of organized
`complexity.
`There have been a number of attempts
`to categorize systems. Perhaps the sim-
`plest and most useful is by P. Checkland,
`who proposes four categories: naturat sys-
`tems, designed physical systems, designed
`abstract systems, and human activity sys-
`tems. He also proposes four concepts that
`aze central to systems thinking:
`"the notion of whole entities which
`have properties as entiries (emergent
`properties ...); the idea that the entities
`are themselves parts'of larger similar enti-
`ties, while possibly containing smaller
`similar entities within themselves (hierar-
`chy ...); the idea that such entities are
`characterized by processes which main-
`tain the entity and its activity in being
`(control ...); and the idea that, whatever
`other processes are necessary in the en-
`
`tity, there will certainly be processes in
`which information is communicated from
`one part to another, at the very min;m~
`this being entailed in the idea `control :'
`system tables The data that collectively
`defines the status of all *resources and all
`*processes within the system. Although
`such data may be represented as tables, it
`maybe more conveniently represented in-
`ternally as linked lists with pointers back
`to associated semaphore variables in some
`cases.
`system testing See ~s~r[xc.
`System V A version of *UNIX.
`systolic array An extension of the
`*pipelining approach to processor design
`where a number of processing elements,
`usually arranged as a one or two-
`dimensional array, form a compound pro-
`cessing unit capable of high throughput.
`The configurarion maybe programmable
`to be optimal for a specific computing re-
`quirement and available memory or ISO
`bandwidth. Such arrays communicate
`with memory or I/O only at their bound-
`aries. Data is `pulsed' from the memory
`into processors) at an array boundary and
`then pulses through the array, undergoing
`processing by each element, until it exits
`at another boundary and is returned to
`memory. Each element of the array can
`contribute to the overall Fxrocessing re-
`quired and hence a high data throughput
`is achievable. The name derives from the
`systolic (pumping) action of the heart.
`
`T
`
`T 1. Symbol for tera-.
`2. A dialect of LISP, similar to *SCHEME.
`tab 1. Short for (a) tabulate, i.e. to lay out
`data; (b) tabulation character, a control
`character used when laying out data to
`control the movement of a print or dis-
`play mechanism. Most keyboards have a
`tab key, which may uutiate the tabulation
`function or maybe used for other control
`purposes.
`2. A feature of many graphical interfaces
`where the user may select one of several
`optional screens by *clicking on the tab.
`The term derives from card indexes
`where a small extension of the card al-
`lows easy identification of the required
`card.
`table A collection of *records. Each
`record may store information associated
`with a key by which specific records are
`found, or the records maybe arranged in
`an *array so that the index is the key. In
`commerdal applications the word table is
`often used as a synonym for matrix or
`may.
`table-driven algorithm An algorithm
`that uses *table lookup.
`table lookup (TLU) A fast method of
`transforming one set of data values into
`another. The target data are stored in the
`form of a *table. In order to perform the
`transformation, a source datum is used to
`index into or seazch the table of target
`data. The resulting target datum is the re-
`sult of the table lookup. See also xwsxixc.
`tablet Short for data tablet
`tabular documentation A method to
`assist with the *documentation of com-
`puting systems using tables. For millennia
`tables have been used to store and display
`large quantities of information. It is pos-
`sible to develop the conception and
`theory of tables beyond the usual idea of
`
`a *table with the needs of displaying for-
`mal information about software and hard-
`ware.
`
`tag 1. To mark in some distinctive fash-
`ion any node in a data structure that has
`been traversed. Using this technique pre-
`cautions can be taken against revisiting
`nodes, e.g. in a circular list.
`2. Short far tag field. A field that is used to
`disc~*n~nate between varianu of the
`same type.
`3. A set of characters used to delineate
`certain types of text in a markup lan-
`guage. For example, in *XML bold text
`would normally be indicated by using the
`tags <b> and ~b>, as in "this word is
`<b>bold<~b>"
`
`tagged architecture A computer archi-
`tecture in which extra data bits are at-
`tached to each word to denote the *data
`type, the function of the word, or both.
`Tagged azchitecture can represent a pow
`erful form of *memory protection, and
`has formed a foundation for certain se-
`cure computer systems based on *hard-
`ware security.
`
`tagged image file format See zzrF.
`
`tail of a list. 1. The last item in a *list
`2. The list remaining when the *head has
`been removed.
`
`tape Either *magnetic tape or *optical
`tape; *paper tape is now obsolete.
`
`tape backup system (TBS) The soft-
`ware, tape drives, and media that form a
`system to back up information held usu-
`ally on disks. Backups aze performed ac-
`cordirig to a number of more or less
`complex regular schemes to ensure maxi-
`mum possibility of restoration in case of a
`breakdown of the primary data store. See
`QISO DUMP.
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