CSE 130   Spring 2010

                                  Lab 5


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

  TA will help you with the following exercise.

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  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. Using for loops

  c    Write a program that reads six integers from keyboard and  prints
       their sum. You must use a for loop.

  d.   Open a pico window.  Part of lab5.c is given here.  Cut and paste
       this  program  in  your pico window.  Save this as lab5.c in your
       directory. Compile and execute. The program just prints value  of
       sum (which is 0).

// lab5.c  March 3, 2010.
// A program to study for loops and break statement.
// Example for class CSE130

   #include <stdio.h>
   int main (void)
    {
      int i, sum = 0;
      int n = 6; // Read six integers.
      int number; // Number to be read from keyboard.

      printf("Sum = %d, Count = %d\n", sum, i);
      return 0;
    }

  e.   We are going to  add  code  to  the  above  program,  just  after
       declarations.   Insert a for loop, that runs from i = 0 to i < n.
       Inside the loop prompt the user for the  next  number.   Read  it
       using scanf. Add it to sum (sum = sum + number).

               printf("Type in a number: ");
               scanf("%d", &number);

  f.   Save, compile and execute. It will ask for six numbers because  n
       is  six.  Type  1   2  3  4  5  6.  Sum printed should be 21, and
       count should be 6.

  3. Modification-I (Break statement)

  g.   Now modify the program as follows.  We want to  get  out  of  the
       loop,  if  user types in a negative number, even if the count has
       not reached 6. Remember, if user does not type  in  any  negative
       number then loop must terminate after six iterations.

  h.   Insert an if statement right after scanf in the loop.
       if (number < 0) break;
       The break statement will get you out of  the  loop.   Since  your
       print statement is after the loop, you will also get the count of
       numbers read. Here count (value of i) will be correct, as you got
       out of the loop before i was updated.

  i.   Save your program, compile and execute.  Try 1, 2,  3,  -4.  Here
       sum should be 6 and count = 3.

  4. Modification-II: Changing to a while loop

  j.   For this modification, replace the for loop by a while loop.  Use
       i as the loop counter for while.

  k.   Initialize i = 0, just before the loop. Condition of  while  loop
       is  (i < n). You need to increment i inside the loop. Do it after
       sum = sum + number.

  l.   Save your program, compile and execute. Try 4, 5, -1. Here sum  =
       9 and count = 2.

  5. Modification-III (Remove break statement)

  m.   Now modify the program such that it does not use break statement,
       but  still uses the while-loop.  Now, if the number read is nega-
       tive ( < 0), then you should not continue with  the  next  itera-
       tion.

  n.   For this, you will need one scanf statement before the  loop  and
       one inside the loop. Do not forget to copy the print statement as
       well that prompts user. This will be before the loop as well.

  o.   Have one more condition for while loop. Include  (number  >=  0).
       Use && connective.

  p.   Delete the break statement. The scanf statement should be at  the
       end  of your loop. As soon as you enter the loop, update sum fol-
       lowed by i++.

  q.   Save, Compile and execute. Try 4, 5, 0, -2.  Here sum should be 9
       and count = 3.