CSE 130   Fall 2009

                                 Lab 7


 DO NOT SUBMIT THIS. THIS IS FOR YOUR PRACTICE ONLY.

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 1. Three parts of Lab7

 -    There are three parts to this exercise. In  the  first  part,  we
      write the average function.  For the second part we change param-
      eters, and in the third we delete the local variable.

 -    Copy lab7.c from this page. Cut and paste it in your pico window.
      Save it as lab7.c.  This program just reads and prints m, n.

// lab7.c
// CSE 130  Lab 7, Oct 21, 2009.
// Sample program for studying functions

   #include <stdio.h>

   // Code for function average.

   int main (void)
    {
      int m, n;

      printf("Type in m, n (both positive)\n");
      scanf("%d%d", &m, &n);
      printf("\nm is %d, and n is %d\n", m, n);

      // Insert code for function call average.
      // Print average of m and n.

      return 0;
    }

 -    Compile lab7.c and execute.

 2. Function average.

 a.   Write an integer function average that calculates average of  two
      integers  and  returns  the  value of type float. Insert code for
      average above main.

 b.   First write the header for function average. What is  its  return
      type? It is float as average could be a decimal number with frac-
      tion.

 c.   How many parameters does it need? It needs two  parameters,  both
      are of type int. Use (int i, int j)

 d.   Store average in variable avg of type float. This is  an  example
      of a local variable.
      avg = (i+j)/2.0;

 e.   You need to declare avg (of type float) in function average.  Add
      a return statement that returns avg.

 f.   From the main program call function average. Get  the  answer  in
      variable b.

 g.   Declare b of type float in main.        b = average(m, n);

 h.   Print b, using a printf statement. For example,
      printf("\nAverage of m and n is: %f\n", b);

 i.   Save, compile and execute. Try m = 5 and n = 6.   Average  should
      be 5.5.

 3. Changing i, j to m, n

 j.   For function average, parameters can be m and n.  But these m and
      n are different from those in main ( ).

 k.   Replace i and j by m and n respectively. Change variables in  the
      body as well.

 l.   Save lab7.c, compile and execute. You should get the same  answer
      that you got for m = 5, and n = 6.

 4. Removing variable avg

 m.   We actually do not need the variable avg, as  we  can  return  an
      expression  of  type float at the end of function average.  There
      is no need to store it in variable avg first.

 n.   Remove declaration for avg. Delete the statement avg = (m+n)/2.0;
      Now at the end, we must return (m+n)/2.0;

 o.   Save your lab7.c program, compile and execute.  Try m = 5 and n =
      6.