CS 99

Summer 2002: HW7 7.18

Tracing, star patterns

Due date: 07.22

1. Objectives
Note that this homework is due a day earlier than usual because of next week’s exam. There is no challenge problem.

Completing all tasks in this assignment will help you:

· trace code by hand

· practice writing nested for loops to demonstrate various output patterns

First skim, and then read the entire assignment before starting.

2.    Tracing
Trace the sequence of assignments to the variables made by the program segment given below, using a new column for each assignment made. The first three assignments have been done for you. You may not need all the columns provided.

n = 57;
x = 0;
y = 1;
while n ~= 0
    if mod( n, 2 ) ~= 0
        n = floor(n/3);
    else
        n = n + 1;
        x = x*9;
        y = y + 10;
    end
end

n:	57
x:		0
y:			1

Write your answers in the table supplied (or a reasonable facsimile) and include it with your other documents.

3. Star Patterns
In the program segments below, you may only use loops, branches, and the following types of fprintf statements:

· fprintf(‘\n’)

· fprintf(‘*’) or fprintf(‘’\\’) or fprintf(‘/’)

· fprintf(‘ ‘) % use two spaces instead of one: things won’t line up properly otherwise

A)     Write a program segment that prompts the user for a non-negative integer n then prints an
           upside-down triangle on the screen. For an input of 4, the segment should print
           * * * *
        * * *
        * *
        *

B) Write a segment that prints a square. For an input of 4, the segment should print

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

C)      Write a segment that prints a square with a diagonal line across its middle. For
           input 5, it should print:

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

D) Finally, write a segment that prints an equilateral triangle. For an input of 6, the segment
should print

* * *

* * * * *

* * * * * * *

* * * * * * * * *

        * * * * * * * * * * *

E)*     See if you can write a segment that prints a diamond. For an input of 5, the segment
           should print

/ \

\ /

\/

*Optional

Copy your program segments into a text file called StarPatterns.doc (or one with another file extension if you are not using Word) and clearly indicate which segment belongs to which part.

4. Submitting your work
Type your name, student ID, and the date at the top of each required document. Print and sign each file. Hand the signed documents to the instructor at the beginning of lecture on Monday 22 July 2002.