C/the.ansi.c.programming.language/c.programming.notes/homework/PS6.html

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   9 <title>Assignment #6</title>
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  11 <body>
  12 <H1>Assignment #6</H1>
  13
  14
  15
  16
  17
  18 <B>Introductory C Programming
  19 <br>
  20 <br>
  21 UW Experimental College
  22 </B><br>
  23 <br>
  24 <B>Assignment #6
  25 </B><p><B>Handouts:
  26 </B></p><p><a href="PS6.html">Assignment #6</a>
  27 <br><a href="PS5a.html">Assignment #5 Answers</a>
  28 <br><a href="http://www.eskimo.com/~scs/cclass/notes/sx11.html">Class Notes, Chapter 11</a>
  29 <br><a href="http://www.eskimo.com/~scs/cclass/notes/sx12.html">Class Notes, Chapters 12</a>
  30 <a href="http://www.eskimo.com/~scs/cclass/notes/sx13.html">and 13</a>
  31 <p><B>Reading Assignment:
  32 </B></p><p><a href="http://www.eskimo.com/~scs/cclass/notes/sx10.html">Class Notes, Chapters 10</a>
  33 <a href="http://www.eskimo.com/~scs/cclass/notes/sx11.html">and 11</a>
  34 <p><B>Review Questions:
  35 </B></p><OL><li>If we say
  36 <pre>
  37         int i = 5;
  38         int *ip = &amp;i;
  39 </pre>
  40 then what is <TT>ip</TT>?
  41 What is its value?
  42 <li>If <TT>ip</TT> is a pointer to an integer, what does <TT>ip++</TT> mean?
  43 What does
  44 <pre>
  45         *ip++ = 0;
  46 </pre>
  47 do?
  48 <li>How much memory does the call <TT>malloc(10)</TT> allocate?  What if
  49 you want enough memory for 10 <TT>int</TT>s?
  50 <li>The assignment in
  51 <pre>
  52         char c;
  53         int *ip = &amp;c;               /* WRONG */
  54 </pre>
  55 is in error; you can't mix <TT>char</TT> pointers and <TT>int</TT> pointers like
  56 this.  How, then, is is possible to write
  57 <pre>
  58         char *cp = malloc(10);
  59         int *ip = malloc(sizeof(int));
  60 </pre>
  61 without error on either line?
  62 </OL><br>
  63 <br>
  64 <p><B>Exercises:
  65 </B></p><OL><li>Write a program to read lines and print only those containing
  66 a certain word.
  67 (For now, the word can be a constant string in the program.)
  68 The basic pattern
  69 (which I have to confess I have parroted exactly from K&amp;R Sec. 4.1)
  70 is
  71 <pre>
  72         while(<I>there's another line</I>)
  73                 {
  74                 if(<I>line contains word</I>)
  75                         <I>print the line</I>;
  76                 }
  77 </pre>
  78 Use the <TT>strstr</TT> function (mentioned in the notes) to look for the
  79 word.  Be sure to include the line
  80 <pre>
  81         #include &lt;string.h&gt;
  82 </pre>
  83 at the top of the source file where you call <TT>strstr</TT>.
  84 <li>Rewrite the checkbook-balancing program from
  85 assignment 4 (exercise 6)
  86 to use the
  87 <TT>getwords</TT> function (from the notes) to make it easy to take the
  88 word ``check'' or ``deposit'', <I>and</I> the amount, from a single line.
  89 <li>Rewrite the line-reversing function from
  90 assignment 4 (exercise 9)
  91 to use pointers.
  92 <li>Rewrite the character-counting function from
  93 assignment 5 (exercise 3)
  94 to use pointers.
  95 <li>Rewrite the string-concatenation program from assignment 5 (exercise 4)
  96 to call <TT>malloc</TT> to allocate a new piece of memory just big enough
  97 for the concatenated result.  Don't forget to leave room for the
  98 <TT>\0!</TT>
  99 <li>Rewrite the string-replacing function from
 100 assignment 5 (exercise 5)
 101 to use pointers.
 102 <li>(harder)
 103 Write a program to read lines of text up to <TT>EOF</TT>, and
 104 then print them out in reverse order.  You can use <TT>getline</TT> to
 105 read each line into a fixed-size array (as we have been doing
 106 all along), but you will have to call <TT>malloc</TT> and make a copy of
 107 each line before you read the next one.  Also, you will have to
 108 use <TT>malloc</TT> and <TT>realloc</TT> to maintain the ``array'' of character pointers
 109 which holds all of the lines.  (Your code will be similar to that
 110 in section 11.3 of the notes, p. 5)
 111 <br>
 112 <br>
 113 Extra credit: remove the restriction imposed by the fixed-size
 114 array into which each line is originally read; allow the program
 115 to accept arbitrarily many arbitrarily-long lines.  (You'll have
 116 to replace <TT>getline</TT> with a dynamically-allocating line-getting
 117 function which calls <TT>malloc</TT> and <TT>realloc</TT>.)
 118 </OL><hr>
 119 <hr>
 120 <p>
 121 This page by <a href="http://www.eskimo.com/~scs/">Steve Summit</a>
 122 // <a href="copyright.html">Copyright</a> 1995-9
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