J-jargon.ltx

\documentclass{wsheet}
\usepackage{rcs}
\usepackage[colorlinks]{hyperref}
\RCS $Id: J-jargon.ltx 239 2010-07-23 21:41:31Z RobPearce $
\RCS $Date: 2010-07-23 22:41:31 +0100 (Fri, 23 Jul 2010) $
\RCS $Revision: 239 $
\sheet{J}{Jargon}
\author{Gareth McCaughan}
\date{Revision \RCSRevision, \RCSDate}
\begin{document}

\section{Credits}

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\copyright{} Gareth McCaughan. All rights reserved.
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This document is part of the LiveWires Python Course. You may
modify and/or distribute this document as long as you comply with the
LiveWires Documentation Licence: you should have received a copy of the
licence when you received this document.

For the \LaTeX{} source of this sheet, and for more information on
LiveWires and on this course, see the LiveWires web site at
\href{http://www.livewires.org.uk/python/}{|http://www.livewires.org.uk/python/|}

%-----------------------------------------------------------------------------
\section{Introduction}
%-----------------------------------------------------------------------------
Computing is full of funny words, and of ordinary words used in
funny ways. We've tried not to use too much jargon in these
sheets, but we haven't always succeeded. So this sheet tries
to give brief descriptions of what some funny words mean. If
you run across something you don't understand, it's worth
taking a quick look at this sheet.

Some of this jargon is general programming jargon. Some is specific
to Python.

Lots of these entries refer to other entries, so if you see a word
in here that you don't understand you should look it up!

\section{The jargon}

\newcommand{\entry}[2]{\vrule width0pt height 12pt\>\emph{#1}\>\parbox[t]{5in}{#2\strut}\\}
\newcommand{\Aentry}[3]{\textbf{\vrule width0pt height 16pt\relax#1}\>\emph{#2}\>\parbox[t]{5in}{#3\strut}\\}

\begin{tabbing}
\qquad\=\textbf{A}\ \ \=\emph{global variable}\ \ \=\+\kill
\Aentry{A}{argument}{An object passed into a function when you
                     call it. It appears inside the function
                     as a local variable.}
\entry{association}{A piece of information that says
                    ``If you're given $X$, give back $Y$''.
                    A dictionary is made up of associations.}
\entry{attribute}{An object that's part of an instance of a class.
                  A little bit like a variable; a little bit like
                  the value in a dictionary association.}
\Aentry{B}{body}{The code inside a loop, or function, or
                 other complicated thing. So a ``function body''
                 is what gets obeyed when you call a function,
                 and a ``loop body'' is what gets obeyed each
                 time around a loop.}
\Aentry{C}{call}{To ``call'' a function is to use it.
                 Calling a function is a bit like copying out its
                 definition and doing that.}
\entry{class}{Classes are kinds of object. (In the real world,
              things like ``computer'' and ``woman'' and ``book''
              are classes.)}
\entry{character}{A letter, digit or other symbol. A string
                  is made up of a sequence of characters.}
\entry{code}{The stuff that programs are made of.
             A ``piece of code'' is a portion of a program.}
\entry{comment}{A piece of a program that doesn't do anything,
                but is just there for people to read. Usually
                the purpose of a comment is to explain what the
                code around it is doing.}
\entry{condition}{Something that might be true or false,
                  like |1>2|.}
\entry{conditional}{Something that depends on a condition,
                    like an |if| statement.}
\Aentry{D}{definition}{A bit of code that tells the computer
                       what something is: what value a variable
                       has, or what a function ought to do, or
                       all about a class.}
\entry{dictionary}{A Python object a bit like a dictionary,
                   an address book or an encyclopaedia.
                   A dictionary is made up of associations.}
\Aentry{E}{element}{An item in a sequence.}
\entry{exception}{An unusual situation in which something has
                  gone wrong, or a Python object describing
                  such a situation. A pretentious way of
                  saying ``error''.}
\entry{expression}{A calculation that produces a value.
                   The simplest expressions are things like
                   constants (|123|, |'eek'|) and variables
                   (|my\_name|). They can get much more complicated:
                   |17*a[a.index(func(99))]>93 and a/(b+c)==2| .}
\Aentry{F}{for loop}{A loop whose body gets obeyed once for
                             each item in a sequence.}
\entry{function}{A set of instructions with a name.
                 You can make the computer obey all the
                 instructions by saying the name of the
                 function.}
\Aentry{G}{global variable}{A variable that exists everywhere
                            in your program, not just inside one
                            function.}
\entry{graphics}{Pictures drawn by a computer.}
\Aentry{I}{immutable}{Not allowed to be changed.}
\entry{import}{To make the things inside a module available
               for use.}
\entry{instance}{An object described by a class. In the real world,
                 computers and women and books are instances of the
                 classes ``computer'', ``woman'' and ``book''.}
\entry{iteration}{A single trip through a loop body.
                  When the loop is obeyed, it will usually
                  go through several iterations.}
\Aentry{K}{key}{One half of an association in a dictionary:
                the half you can look things up by. If you say
                |dict['zog']123|, then the key is |'zog'|.}
\Aentry{L}{list}{An object made up of some number of other objects,
                         in order. You can get at them by number.}
\entry{local variable}{A variable that exists only inside
                                   a particular function, not affecting
                                   anything outside the function.}
\entry{loop}{A piece of your program that might get obeyed
                         over and over again.}
\Aentry{M}{module}{A bunch of objects with names that you can
                           ``import'' into your program.}
\Aentry{O}{object}{Any piece of information Python can work with,
                           like a number or string or list.}
\Aentry{R}{read}{To get information into a program. For instance,
                         if you ask the person sitting in front of the
                         computer to type something in, that's ``reading''.}
\entry{return}{What a function does when it's finished.
                           If it ``returns a value'', then the function
                           call can be used in an expression.}
\Aentry{S}{sequence}{A list or string or tuple. (Actually there are
                     other kinds of sequence, but you don't need to
                     worry about those.)}
\entry{string}{A sequence of characters, usually forming a piece of text.}
\entry{subclass}{A class, all of whose instances are also instances
                 of another class. In the real world, ``Apple Macintosh''
                 is a subclass of ``computer'', which is a subclass of
                 ``electronic device'', which is a subclass of ``thing''.}
\Aentry{T}{tuple}{A particular kind of sequence, written like
                  this: |(1,2,3)| . Unlike lists, tuples are
                  immutable.}
\Aentry{V}{value}{An object. The result of a calculation,
                  or of a function call, or of referring
                  to a variable. Also: one half of an association
                  in a dictionary: the half you're looking for when 
                  you do a lookup. If you say |dict['zog']=123|, then
                  the value is |123|.}
\entry{variable}{A name for an object.
                 After saying |x=6|, |x| is a name for the
                 object usually known as |6|, and using |x|
                 will usually do the same as using |6| would.
                 |x| is called a ``variable'' because you can
                 change what object it names.}
\end{tabbing}
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\end{document}