lang/C/the.ansi.c.programming.language/c.programming.notes/homework/PS5.html

   1 <!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
   2 <!-- This collection of hypertext pages is Copyright 1995-7 by Steve Summit. -->
   3 <!-- This material may be freely redistributed and used -->
   4 <!-- but may not be republished or sold without permission. -->
   5 <html>
   6 <head>
   7 <link rev="owner" href="mailto:scs@eskimo.com">
   8 <link rev="made" href="mailto:scs@eskimo.com">
   9 <title>Assignment #5</title>
  10 </head>
  11 <body>
  12 <H1>Assignment #5</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 #5
  25 </B><p><B>Handouts:
  26 </B></p><p><a href="PS5.html">Assignment #5</a>
  27 <br><a href="PS4a.html">Answers to Assignment #4</a>
  28 <br><a href="http://www.eskimo.com/~scs/cclass/notes/sx9.html">Class Notes, Chapter 9</a>
  29 <br><a href="http://www.eskimo.com/~scs/cclass/notes/sx10.html">Class Notes, Chapter 10</a>
  30 <p><B>Reading Assignment:
  31 </B></p><p><a href="http://www.eskimo.com/~scs/cclass/notes/sx9.html">Class Notes, Chapter 9</a>
  32 <p><B>Review Questions:
  33 </B></p><OL><li>What's wrong with this <TT>#define</TT> line?
  34 <pre>
  35         #define N 10;
  36 </pre>
  37 <li>Suppose you defined the macro
  38 <pre>
  39         #define SIX 2*3
  40 </pre>
  41 Then, suppose you used it in another expression:
  42 <pre>
  43         int x = 12 / SIX;
  44 </pre>
  45 What value would <TT>x</TT> be set to?
  46 <li>If the header file <TT>x.h</TT> contains an external prototype declaration
  47 for a function <TT>q()</TT>,
  48 where should <TT>x.h</TT> be included?
  49 <li>(harder)
  50 How many differences can you think of between <TT>i</TT> and
  51 <TT>J</TT> as defined by
  52 these two lines?
  53 <pre>
  54         int i = 10;
  55         #define J 10
  56 </pre>
  57 (Hint: think about trying to write <TT>J = 5</TT>, or <TT>int a[i]</TT>.)
  58 </OL><br>
  59 <br>
  60 <p><B>Exercises:
  61 </B></p><OL><li>Pick one of the programs we've worked with so far
  62 that uses the <TT>getline</TT> function,
  63 such as the <TT>getline</TT> test program
  64
  65 (assignment 4, exercise 2)
  66 or the ``word zipping'' program
  67
  68 (assignment 4, tutorial 3)
  69 or the checkbook balancing program
  70
  71 (assignment 4, exercise 6).
  72
  73 Arrange the program in two source files,
  74 one containing <TT>main()</TT>,
  75 and one containing <TT>getline()</TT>.
  76 If possible, set your compiler to warn you
  77 when functions are called or defined without a prototype in scope.
  78 Create a header file <TT>getline.h</TT>
  79 containing the external function prototype for <TT>getline()</TT>,
  80 and <TT>#include</TT> it as you see fit.
  81 Also use a preprocessor macro such as <TT>MAXLINE</TT>
  82 for the maximum line length
  83 (i.e. in declarations of <TT>line</TT> arrays,
  84 and calls to <TT>getline</TT>).
  85 <li>Write a program to read its input and write it out, double-spaced
  86 (that is, with an extra blank line between each line).
  87 Process the input a character at a time;
  88 do <em>not</em> read
  89 entire lines at a time
  90 using <TT>getline</TT>.
  91 <li>Write the function
  92 <pre>
  93         int countchars(char string[], int ch);
  94 </pre>
  95 which returns the number of times the character <TT>ch</TT> appears in the
  96 <TT>string</TT>.
  97 For example, the call
  98 <pre>
  99         countchars("Hello, world!", 'o')
 100 </pre>
 101 would return 2.
 102 <li>Write a short program to read two lines of text, and concatenate
 103 them using <TT>strcat</TT>.  Since <TT>strcat</TT> concatenates in-place, you'll
 104 have to make sure you have enough memory to hold the concatenated
 105 copy.  For now, use a <TT>char</TT> array which is twice as big as either
 106 of the arrays you use for reading the two lines.  Use <TT>strcpy</TT> to
 107 copy the first string to the destination array, and <TT>strcat</TT> to
 108 append the second one.
 109 <li>Write the function
 110 <pre>
 111         replace(char string[], char from[], char to[])
 112 </pre>
 113 which finds the string <TT>from</TT> in the string <TT>string</TT>
 114
 115 and replaces
 116 it with the string <TT>to</TT>.
 117 You may assume that <TT>from</TT>
 118 and <TT>to</TT> are the same length.  For example, the code
 119 <pre>
 120         char string[] = "recieve";
 121         replace(string, "ie", "ei");
 122 </pre>
 123 should change <TT>string</TT> to <TT>"receive"</TT>.
 124 <br>
 125 <br>
 126 (Extra credit:
 127 Think about what <TT>replace()</TT> should do
 128 if the <TT>from</TT> string appears multiple times
 129 in the input string.)
 130 </OL><hr>
 131 <hr>
 132 <p>
 133 This page by <a href="http://www.eskimo.com/~scs/">Steve Summit</a>
 134 // <a href="copyright.html">Copyright</a> 1995-9
 135 // <a href="mailto:scs@eskimo.com">mail feedback</a>
 136 </p>
 137 </body>
 138 </html>