Assignment 1, due Jan 20

Solutions

Part of the homework for CS:2820, Spring 2017
by Douglas W. Jones
THE UNIVERSITY OF IOWA Department of Computer Science

  1. A test of your understanding of the prerequisites: Consider this recursive integer function. All operators here are integer operations. This is an informal mathematical definition; it is not coded in a programming language:

    if i < 3, f( i ) = i
    otherwise f( i ) = f( i – 1 ) + f( i – 3 )

    A Question: Give the values of f(0) through f(9). (1.0 point)

    f(0) = 0
    f(1) = 1
    f(2) = 2
    f(3) = 2
    f(4) = 3
    f(5) = 5
    f(6) = 7
    f(7) = 10
    f(8) = 15
    f(9) = 22

  2. Background: If you do not have a CLAS Linux account, create one. The instructions are here:
      — http://www.divms.uiowa.edu/clas_linux/
    Follow the instructions there for "Create a CLAS Account". Note that this is easier from on campus, for example, in one of the Information Technology Centers, because if you are off campus, you will have to tunnel through the University's firewall using a VPN. (The link for how to set that up is there too, but it will take time, so don't let the VPN issue slow you down.)

    Use your account to sign in to linux.cs.uiowa.edu using either an SSH client or FastX

    You can get to FastX with the following link:
      — http://fastx.divms.uiowa.edu
    Note that FastX just opens a remote Linux desktop. If you use the XFCE desktop, you can open a terminal window to get to the same command line interface that you use with an SSH session.

    To make an SSH connection directly from a Mac or Linux system, open a terminal window locally (terminal is an application, a system utility), then type this command
        ssh linux.cs.uiowa.edu -l HawkID
    with your own HawkID substituted for HawkID in the command. Access from off-campus requires an additonal parameter. We will discuss this in class. It is almost as easy from a PC, where you must launch either the PuTTY or SecureCRT application and then fill in a form with the system name and HawkID.

    For additional guidance, see:
      — http://www.divms.uiowa.edu/clas_linux/help/start/remote.html

    A question: Use a shell window on the CS Linux machine. Type the following command:
      [HawkID@serv16 ~]$ ~dwjones/object
    (Boldface in the above is the command you type, non-bold is the prompt from the system; type the requested text verbatim, do not change a thing.) Report the output you got. If you did not make it all the way to the point where you could do the above, report how far you got. (1 point)

    The expected output was something like this: 

    CS:2820 welcome script for HawkId, Thu Jan 26 14:02:09 CST 2017.

    Unfortunately, due to a change made by the system administrators without informing the faculty, the HawkId was omitted for newly created Linux accounts.

    88 people ran this script. The script was run 177 times, so many students ran it many times.

  3. Background: In the introduction to the textbook, there is a section entitled Source Code. There is a block quotation in this section that is almost 2 pages long.

    A question: What is it? (do not copy it, tell what it in just a few words.)

    The long block quotation is the copyright notice that applies to all of the the code given in the the book's web site.