CSE 130   Fall 2009

                                 Lab 9


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

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 1. Structures

 -    This exercise is about structures and how to use  them  in  func-
      tions.  Study  the global definition structure `tm' given to you.
      It has been renamed as time using typdef. See that  statement  as
      well.  This structure has been declared above main, so it is glo-
      bal to all functions (available everywhere).

 -    Copy lab9.c from this page. Cut and paste it in your pico window.

// lab9.c
// CSE 130 Fall 2009. Lab 9, Nov 12, 2009.
// Sample program for studying structures and functions

// Global declaration for type time.

   #include <stdio.h>

   struct tm   // struct tm will be redefined as time
    { int hours;
      int minutes; };  // Seconds are not included.

   typedef struct tm time;  // This defines time.

   // time is another name for type struct tm.
   // Now type time is available to all functions.

   // Code for function add

   // Code for function rownd

   // Code for allHours

   int main (void)
    {
      //  Declare structure variables a, b for
      //  time duration-1 and duration-2.
      //  Additional Variable declarations .

      printf("Type in duration-1 as hours and minutes.\n");
      scanf ("%d%d", &a.hours, &a.minutes );

      printf("Type in duration-2 as hours and minutes.\n");
      scanf ("%d%d", &b.hours, &b.minutes );

      // Call functions as required and print results.

      return 0;
    }

 -    After pasting it in pico window, save it as lab9.c.  Do not  com-
      pile.  Insert  declaration  for  a, b. Both are of type time. Now
      compile and execute. The program will ask for durations a and  b.
      Just  type  in  some values.  Program will end without doing any-
      thing, as there are no additional statements.

 2. Function add

 a.   Write code for function add that takes two arguments x, y of type
      time.  It  adds them and returns the result as a structure.  This
      code should be in its place indicated by the comment above
      main( ).

 b.   First write the header for add. What is its type?   What  is  the
      type of its arguments?

 c    You will need a local variable c  of  type  time.   Declare  that
      inside  the  body of `add'.  Now calculate c.hours and c.minutes.
      Handle the case if c.minutes exceed 59.

 d.   Return c at the end. Enclose the body with { }.

 e.   In the main program, insert a call to function  add.   Parameters
      are  a,  b. Get the result back in another variable of type time.
      You may use c again. Declare c of type time.

 f.   Insert a print statement for printing c.hours and c.minutes.  See
      scanf statement for some hints.

 g.   Save, compile and execute. Does it print addition  of  two  dura-
      tions?  Test  with a = 20 87 and b = 01 45 Here answer will be 22
      hours and 32 minutes.

 3. The function rownd.

 h    This function rounds  a  given  time  duration  and  returns  the
      rounded value as an integer hours. It has one parameter x of type
      time.  This code should be in its place indicated  for  round  by
      the comment above main( ).

 i.   First write the header for round. What is its type?  What is  the
      type of its argument?

 j    You will need a local variable  i  of  type  int.   Declare  that
      inside  the  body  of  `round'.   Calculate  i  as  follows.   if
      x.minutes < 30 then i = x.hours else i = x.hours + 1;

 k.   Return i at the end. Close the body.

 l.   In the main program, insert two calls to function rownd.  One for
      duration  a  and  one for duration b. To save typing extra state-
      ments, have these calls in the printf statement itself. For exam-
      ple,         printf("\nRounded time a is: %d", \n rownd(a));
      Insert one for b as well.

 m.   Save, compile and execute. Does it print rounded values for dura-
      tions  a  and  b?  Test with a = 20 47 and b = 01 15 Here rounded
      time duration a is 21 and that for b is 1.

 4. Function allHours

 n    This function converts the given duration to a decimal  value  in
      hours  and  returns  it. Type of returned value is float.  It has
      one parameter x of type time.  This code should be in  its  place
      indicated for allHours by the comment above main().

 o.   First write the header for allHours. What is its type?   What  is
      the type of its argument?

 p    You will need a local variable f of  type  float.   Declare  that
      inside  the  body  of  `allHours'  Calculate  f  as follows.
      f =  (float)x.hours + (float)x.minutes/60.0;

 q.   Return f at the end. Close the body.  See  if  you  can  do  this
      without  declaring  f.   Just  use  the expression in your return
      statement.

 r.   In the main program, insert two  calls  to  function  `allHours'.
      One  for  duration a and one for duration b. To save typing extra
      statements, have these calls in the printf statement itself.  For
      example,
      printf("\nDuration in hours for a is: %f", \n allHours(a));
      Insert one for b as well.

 m.   Save, compile and execute. Does it print decimal values for dura-
      tions  a  and  b?  Test with a = 20 47 and b = 01 15 Here decimal
      duration for a is 20.7833 and that for b is 1.25.