CSE 130   Spring 2010

                                  Lab 4


  PLEASE DO NOT SUBMIT LAB EXERCISES. They are for your practice only.

  TA will help you with the following exercise.

  ----------------------------------------------------------------------

  1. Using bash

  a.   After you sign in, type a command `bash' (without  quotes).  With
       this  backspace key will work.  All other UNIX commands will work
       as before.  A list of UNIX command is on the course webpage.

  b.   When you are done, type exit to get out of bash.  Do not do  that
       right now.  Type logout to disconnect from sparky.

  2. Nested while loops

  c.   Cut and paste this program in your pico  window.   Save  this  as
       lab4.c  in  your directory. Compile and execute. The program just
       echoes values of m and n that you typed.

// lab4.c  Feb 24, 2010.
// A program to study nested while loops.
// Example for class CSE130

   #include <stdio.h>

   int main (void)
    {
      int m, n
      printf("Type in m, n on the same line. Let m > n.\n");
      scanf ("%d%d", &m, &n);
      printf("\nm = %d,  n = %d\n\n", m, n);

// Insert code in the space below for nested loops.
// Do this step by step. Do the inner loop first.



      return 0;

    }


  d.   We are going to add code to the above  program,  just  after  the
       second  printf  statement  to print a rectangle of m rows (lines)
       with n stars (*) on each line. TA will explain loop structure  on
       white-board.

  e.   For this purpose we will write two nested while loops with i  and
       j  as two loop counters. Outer loop runs from i = 1 to m printing
       m rows of stars. Inner while loop prints n stars on each line. It
       runs from j = 1 to n.  Declare and initialize i, j properly. Also
       print \n at correct places.

  f.   To do this step by step, first write the inner  while  loop  that
       prints  a  line  (or just one row of stars). Use n here.  Cut and
       paste this code to your PICO  window,  after  the  second  printf
       statement.

  g.   Fill in the condition of while loop, and printf statement.  After
       the loop, print \n.

              j = 1;
              while (       )
                { printf (      );
                  j = j+1;
                }

  h.   Save compile and execute. It will ask for both m and n. Type m  =
       4 and n = 3. The program should print one line of 3 stars.

  i.   Now add the outer while loop. What  is  the  condition  of  outer
       loop?  Do not forget to initialize i = 1; or something like that.
       Also you need to increment i (i++;) in  the  body  of  the  outer
       loop.

  j.   Save your program, compile and execute.  If m = 4, and n = 3 then
       rectangle would be like:

       ***
       ***
       ***
       ***

  3. Modification-I: Printing a right angle triangle:

  k.   For this we print 1 star on the first line, 2 stars on the second
       and  so  on. On the last line print m stars. We need only m. Pro-
       gram will ask for m and n both. That is ok. Type in both. Just DO
       NOT USE n.

  l.   The outer loop runs from i = 1 to m. Keep that  as  it  is.   The
       inner  loop  prints  m  stars  for the mth iteration of the outer
       loop. Be careful with modifying the inner loop. We use j for  the
       inner  loop.  But  the  loop  runs from j = 1 to j = m and not n.
       Change the condition of inner while-loop.

  m.   For m = 4, triangle would look like:

       *
       **
       ***
       ****

  n.   Do not use for or do-while loops. You MUST use while loops.

  4. An if-else statement (if you have time)

  o.   TA will tell you how to write an `if' statement for checking if m
       is  indeed  greater  than  n.   Print proper message such as m is
       greater than n or m is not greater than n.
       // An if-else  statement

          if (     )  printf ("m is greater than n. \n");

               else  printf ("m is not greater than n. \n");


  p.   Insert an if-else statement after nested while loops.

  q.   Save, Compile and execute. Try different values of m.   Here  you
       need to type in n also. See if your if statement works correctly.

  r.   Try m = 4, n = 3. Also try m = 5, n = 8. Remember every time  you
       execute start with ./a.out