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   9 <title>section 2.3: Constants</title>
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  15 <H2>section 2.3: Constants</H2>
  16
  17 page 37
  18 <p>We write constants in decimal, octal, or hexadecimal
  19 for our convenience,
  20 not the compiler's.
  21 The compiler doesn't care;
  22 it always converts everything into binary internally, anyway.
  23 (There is, however,
  24 no good way to specify constants in source code in binary.)
  25 </p><p>pages 37-38
  26 </p><p>Read the descriptions of character and string constants carefully;
  27 most C programs work with these data types a lot,
  28 and their proper use must be kept in mind.
  29 Note particularly these facts:
  30 </p><OL><li>The character constant <TT>'x'</TT> is quite different from
  31 the string constant <TT>"x"</TT>.
  32 <li>The value of a character is simply
  33 ``the numeric value of the character in the machine's character set.''
  34
  35 <li>Strings are terminated by the null character, <TT>\0</TT>.
  36 (This applies to both string constants and to all other strings
  37 we'll build and manipulate.)
  38 This means that the size of a string
  39 (the number of <TT>char</TT>'s worth of memory it occupies)
  40 is always one more than its length
  41 (i.e. as reported by <TT>strlen</TT>)
  42 appears to be.
  43 </OL><p>As we saw in section 1.6 on page 23,
  44 it's possible to switch rather freely between thinking of a
  45 character as a character and thinking of it as its value.
  46 For example, the <em>character</em> <TT>'0'</TT>
  47 (that is,
  48 the character that can print on your screen
  49 and looks like the number zero)
  50 has in the ASCII character set the internal <em>value</em> 48.
  51 Another way of saying this is to notice that the following
  52 expressions are all true:
  53 <pre>   '0' == 48
  54         '0' == '\060'
  55         '0' == '\x30'
  56 </pre>We'll have a bit more to say about characters
  57 and their small integer representations
  58 in section 2.7.
  59 </p><p>Note also that the <em>string</em> <TT>"48"</TT> consists of the
  60 three characters <TT>'4'</TT>, <TT>'8'</TT>, and <TT>'\0'</TT>.
  61 Also in section 2.7
  62 we'll meet the <TT>atoi</TT> function
  63 which computes a numeric value from a string of digits like this.
  64 </p><p>page 39
  65 </p><p>We won't be using enumerations,
  66 so you don't have to worry too much about the description of
  67 enumeration constants.
  68 </p><hr>
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  77 This page by <a href="http://www.eskimo.com/~scs/">Steve Summit</a>
  78 // <a href="copyright.html">Copyright</a> 1995, 1996
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