CSE 130  Fall 2009

                                 Lab 2


 NOTE: It is very important for this course that you  obtain  a  sparky
 account (ic.sunysb.edu) for completing assignments. It is same as your
 NetID.  If it is not working, visit the SINC site in the main  library
 building and speak to a representative to resolve the issue.

 TA will help you with the following skills:

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

 1. Review of lab1.c program (Same as Lab1 document)

 a.   If you created the directory cse130,  then  change  your  working
      directory to cse130 (command cd).

 b.   The program is given here, but use your name, and your id number.
      You  may  use  PICO to type the following program in. But it will
      save you a lot of time if you just cut and paste  this  from  the
      CSE 130 webpage to your PICO window.

// lab1.c
// CSE 130 Fall 2009. Lab 1, Sept 9, 2009.
// Shaunak Pawagi, Id-No: xxx-yy-zzzz
// Sample program to print two lines.

   #include <stdio.h>

   int main (void)
     {
       printf ("These lines are printed by\n");
       printf ("the lab1.c program.\n");
       return 0;
     }

 c.   Use `ls' to see that it is there.  If  not,  follow  instructions
      from Lab1 document to create this file.

 d.   Compile the C program by typing the Unix command gcc lab1.c
      (Typically the compiler produces some error messages here,  indi-
      cating  that  some  statements  are not correct; if so go back to
      step f and fix the the errors.)

 e.   Use `ls' to see that the gcc command created  a  new  file  named
      a.out

 f.   Run your program by typing the command ./a.out

 g.   You should see it output the two lines of text.

 2. Handing in e-copy of your C program.

 i.   Your first C program is in file lab1.c.  Please  make  sure  that
      every  program  you  submit, has your name, ID and program number
      right at the beginning as shown in the example (as comments).

 j.   Use command `more lab1.c' (without quotes) to display it on  your
      screen. Check that it has your name, ID etc. at the beginning.

 k.   Execute ~cse130/submit command to hand an e-copy of this file.

 l.   Respond to questions, and when asked for file-name, type ./lab1.c

 m.   If your submission is successful, you will get an acknowledgement
      right away.

 n.   Use the option to check on your submission.

 3. Another program lab2.c

 o.   Open a pico window. Cut and paste lab2.c program  from  the  web-
      page. Save it as lab2.c.

 p.   Compile your program using gcc and execute using ./a.out command.

 q.   It should output 1 2 3 4 5 6 7 8 9 10.

// lab2.c
// Sample program to print: 1 2 3 4 5 6 7 8 9 10.
// Example for class CSE130.
// We print i using printf function.
// Use of %d will be explained later.
// There is a space before % character.

   #include <stdio.h>
   main ( )
    { int i = 1;
      while (i <= 10)
        { printf(" %d", i);
          i=i+1;
        }
      printf(".\n");
    }

 r.   Program lab2.c has a while loop.  When executed, this loop prints
      the  numbers  from  1  to  10  (on  one  line).  The while (test-
      condition) {.. body ..} statement causes the {.. body ..}  to  be
      repeated  as  long as the (condition) is true. The combination <=
      is how one types "less than or equals".

 s.   The int i=1; collapses two statements: int i;  means  that  i  is
      declared  to  be  an  integer variable, and i=1; is an assignment
      statement setting an initial value of one to i.

 t.   Note that main has not been  declared  as  an  integer  function.
      Also  return 0; statement is missing. Some C compiler assume that
      main () is an integer function, and there is no need for explicit
      declaration.  But if you declared main to be an integer function,
      then return 0; statement is required at the end.  Also  there  is
      no need to have (void) declaration for main; it is optional.

 4. Modifications to the above program

 u.   Modify the program so it outputs the positive numbers counting by
      fives  up  to 100, namely: 5, 10, 15, 20, ..., 100.  Initialize i
      to 5. Change the condition to (i  <=  100).   Increment  i  by  5
      inside the loop.  You DO NOT have to modify the printf statement.
      Compile your program and execute it (type ./a.out).

 v.   Another Modification: Change the program so it counts  down  from
      20  to 0, printing only the even numbers: 20 18 16 14 12 10 8 6 4
      2 0. Set i = 20; Let condition be (i >= 0), and have i = i-2;  in
      the  body  of  the loop.  Here also you do not need to modify the
      printf statement.  Again, compile your program and execute it.

 5. Infinite loop:

 w.   Now we will study an infinite or unterminated loop.

 x.   Note that i has been set to 20. Keep the condition (i  >=  0)  as
      is. Replace i = i-2; by i = i+2;

 y.   Since i is 20 to start with,  program  prints  20,  22,  24,  26,
      ......  but  does  not  end,  since i will remain above 0 all the
      time.

 z.   To stop execution type ^c (control-c). This  will  terminate  the
      program.

 6. Reading input from keyboard:

 -    Fix the program by changing i = i+2; back to i = i-2;

 -    In the above program we count down from 20. But the value  20  is
      assigned  to  variable  i in the program.  But we can get it from
      user as well, by using a scanf statement.

 -    Remove i=20; statement and insert these two in its place.

              printf("Type in an integer value for i: ");
              scanf("%d", &i);

 -    Compile your program using gcc  and  execute.  During  execution,
      your  program will print the message Type in an integer value for
      i: and will wait for your response.

 -    Type 10 and see what happens. Execute again.  Type  45,  and  see
      what it prints.