CMSC216 HW01: C Basics

                           _________________

                            HW 01 QUESTIONS
                           _________________


Write your answers to the questions below directly in this text file to
prepare for the associated quiz. Credit for the HW is earned by
completing the associated online quiz on Gradescope.


ADVISORY: HW is PRACTICE
========================

  HWs are practice.  To earn credit for doing this HW, you will at some
  point visit Gradescope and take an online quiz which asks about items
  studied in the HW; the multiple choice quiz will inform you of
  correct/incorrect answers making it hard not get full credit.

  In the spaces below you'll be asked to "write your answer" or "do this
  and paste what you see." No staff will check these answers except if
  you want them. Credit for the HW is earned through the online quiz,
  not writing answers to the questions. Solutions to the HW will also be
  posted some time after the due date.

  Knowing that your written answers won't be checked may disincline you
  to actually write anything down. Just keep in mind that exam questions
  are similar but more difficult and WILL require you to write an
  answer. That makes HW a good chance to practice studying code, editing
  it, running it, and writing about it.  Writing down your answers will
  also make it quick and simple to get full credit on the multiple
  choice quiz questions for the HW as they are easier to solve than full
  written answers. Finally, it's a great tactic to write your own
  answers, then compare then later to the provided solutions as a means
  to study and identify weak points in your understanding.

  Office hours or discussion sections are a good time to chat up a staff
  member if you are perplexed by HW content. Students sometimes approach
  staff and ask for extra practice problems. They will be asked, "sure,
  but first show me your written answers to the last few HWs."  In 6
  semesters, staff have not yet needed to create more practice problems
  as students asking for them invariably skipped doing the provided HW
  problems.


PROBLEM 1 `age.c'
=================

A
~

  Examine the source code for `age.c'. Compile it using the following
  invocation of `gcc'
  ,----
  | gcc age.c
  `----
  This should create the executable `a.out'. Run this program using the
  invocation.
  ,----
  | ./a.out
  `----
  Perform several runs of the program with the following values and
  paste your output in the space below.
  - Enter 16
  - Enter 18
  - Enter 25
  - Enter 44


B
~

  Analyze the code for `age.c' and describe a flaw in the conditional
  structure towards the end that prevents the output:
  ,----
  | You can vote, drink, and be president.
  | Try all three at once!
  `----
  from being printed.

  Alter the code to fix this bug so that for ages 35 and larger, the
  above text is printed. Paste your fixed code for the conditional below
  and test it by recompiling and showing a demo run.


C
~

  Attempt to enter some absurd ages for the age computation.
  - Enter 5000
  - Enter -5000
  Describe anything strange that seems to be happening based your
  understanding of how basic arithmetic is supposed to work.

  If you happen to know WHY this strangeness is happening, describe it
  below.  If not, you will find out soon.


D
~

  Describe which function is used to print information to the screen.
  Describe how it seems to work to substitute values into output and
  what *format specifier* indicates an integer should be substituted.


E
~

  Describe what function is used to read typed input interactively from
  a user in the `age.c' program.  Describe anything that seems strange
  about this function or its arguments.

  We will learn in not long why this bit of strangeness is necessary.


PROBLEM 2 Collatz
=================

A
~

  Examine and compile the code associated with the collatz
  program. There are three files associated with this program.
  - `collatz_funcs.c' which defines two utility functions for computing
    the Collatz sequence
  - `collatz_main.c' which defines a `main()' function to compute a
    Collatz sequence
  - `collatz.h' header file which declares functions in
    `collatz_funcs.c' so that they are known to `collatz_main.c'

  To compile the program, use the following invocation of `gcc'
  ,----
  | gcc -o collatz collatz_funcs.c collatz_main.c
  `----
  This should create the program `collatz' which can be run with
  ,----
  | ./collatz
  `----

  Do so and enter inputs
  - Starting integer 7
  - Show output: 1

  Paste the output below.


B
~

  Determine what the "dash-O" option used above for `gcc -o' does. For
  example, what happens if one runs
  ,----
  | gcc -o GLIPGLOP collatz_funcs.c collatz_main.c
  `----

  instead.  You may wish to use the `ls' command to list the files in
  the current directory.

  Describe what happens if you omit this option `-o' when compiling as
  in
  ,----
  | gcc collatz_funcs.c collatz_main.c
  `----


C
~

  Attempt to compile only the file `collatz_main.c' by doing
  ,----
  | gcc -o something collatz_main.c
  `----


  This should result in an error. Show the output of that error and
  determine why the compilation fails.


D
~

  Attempt to compile only the file `collatz_funcs.c' by doing
  ,----
  | gcc -o something collatz_funcs.c
  `----


  This should result in an error. Show the output of that error and
  determine why the compilation fails.


Review Course Syllabus
======================

  Make sure to review the Course Syllabus to acquaint yourself with
  course policies such as the following.
  - The PRIME DIRECTIVE to preserve academic integrity
  - Fair collaboration with other students
  - Late submission policies on assignments (projects, HW, quizzes, lab
    work)
  - Grading criteria and weighting on exams/assignments