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<p class=MsoNormal><span style='color:#1F497D'>Well yes, and no. Thanks for the
very clear description of a record which IS an array (is ISBN an integer or a
string? PHP will treat it contextually)! However this does not take away from
the fact that some major modern languages are not strongly typed and so the
study guide distinction does not apply and this disadvantages students working
in those languages.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Laurie<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> sofdev-bounces@edulists.com.au
[mailto:sofdev-bounces@edulists.com.au] <b>On Behalf Of </b>Steven Bird<br>
<b>Sent:</b> Wednesday, 18 August 2010 8:58 PM<br>
<b>To:</b> Year 12 Software Development Teachers' Mailing List<br>
<b>Subject:</b> Re: [Year 12 SofDev] Records and Arrays<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The following might help you to distinguish these concepts.<br>
<br>
Consider any kind of real world entity, e.g. a student, a school, a book, a
patient, etc. Now think about its attributes. For a book this might
be title, author, year, isbn, price... When we model such an entity using
a computer, we specify a set of attributes. This is a
"record". It is just a collection of attributes describing an
entity.<br>
<br>
A record could be stored on disk (e.g. as a row of a relational database table,
or as a row of a CSV file), or represented in volatile memory in a data
structure in a running program. Perhaps the most common data type used
for representing a record is an "associative array" ("hash"
in Perl; "dictionary" in Python; "array" (!) in PHP,
"map" in C++); some languages support a "tuple" type which
is also appropriate for representing records. However, at one level these
details don't matter. What's important is just that we have a set of
attributes.<br>
<br>
Now consider any collection of entities of the same type, e.g. students,
schools, books, patients, etc. When we model these in a computer, we
specify a collection of like entities. This is just a set or list of
entities.<br>
<br>
This list could be stored on disk (e.g. as a relational table, or a CSV file),
or represented in a running program. The most common data type is an
"array", and that's what it is called in most languages (but it is
"list" in Python). Some languages encourage you to define array
elements to be all of the same type, but not all. In general, I think
this is a good practice.<br>
<br>
PHP blurs the distinction between records and arrays. However, a
programmer can use <span style='font-size:10.0pt'>PHP</span> in such a way to
keep them quite distinct:<o:p></o:p></p>
<pre>my_record1 = array('isbn'=>1441412050, 'title'=>'Alice in Wonderland', 'author'=>'Lewis Carroll');<br>
<br>
<o:p></o:p></pre><pre>my_record2 = array('isbn'=>1441412050, 'title'=>'Through the Looking Glass', 'author'=>'Lewis Carroll');<br>
<br>
my_array = array(my_record1, my_record2);<br>
<br>
<br>
<o:p></o:p></pre><pre style='margin-bottom:12.0pt'><br>
my_record1['isbn']; /* access a record's attribute by name */ <br>
my_array[1]; /* access an array's element by index */<o:p></o:p></pre>
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<p class=MsoNormal style='margin-bottom:12.0pt'>I hope this helps!<br>
<br>
--<br>
Steven Bird<br>
<a href="http://stevenbird.me/">http://stevenbird.me/</a><o:p></o:p></p>
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