You Must Show Your Work for Full Credit

Computer Science240Name: KEY

Section 01

EXAM 01

February01, 2008

This exam has 4 pages, including this cover page. Please make sure you have all 4 pages.

You have 55 minutes to complete this exam.

You must show your work for full credit.

[2 pts each] 1. Answer the following:

(a) Explain what we mean by software engineering.

Software engineering is a disciplined approach to the creation of maintenance of computer programs.

(b) Give an example of an abstraction (we discussed a couple in class).

A map. A computer program.

ADT = Abstract Data Type. A data type whose properties (domain and operations) are specified independently

Of any particular implementation. All Java built-in types are ADTs, and the Java class mechanism can be used to build ADTs.

(d) What are Agile Methods?

Today it is often important for software to be developed quickly so as to meet a pressing need or to provide leverage in a rapidly changing world. Classic software engineering methods don’t typically work under these conditions. A collection of “agile” or “lightweight” methods has recently been identified to help with quick software development.

2. [2 pts each] Describe the order of magnitude of each of the following functions using Big-O notation:

(a) N2+N3(b) N*logN+N2(c) N*(N+1)/2(d) N2*logN + N(e) 2N + N2

O(N3)O(N2)O(N2)O(N2logN)O(2N)

[3 pts each] Describe the order of magnitude of each of the following code sections, using Big-O notation:

(f)(g)

count = 0;count=0;

for (int i=0; iN; i=i+2)for (int i =0; i < N; i++) {

count++; value = N; O(N) while ( value > 1) {

value = value / 2;

count++;

}

}O(N*logN)

(h)

count = 0;

for (int i=0; iN; i++) {

for (int j=i; j<N; j++) {

count++;

O(N2)
[2 pts each] 3. Explain, or give the Unix commandfor the following(you only need to give onepossible solution):

(a) Give a command which would change your current directory

to your home directorycd or cd ~

(b) Briefly explain how is ls –Fdifferent thanlsls –F shows executables * and

directories with a /

(d) Output a file Date.java to the c102 printerenscript -2r –Pc102 Date.java

lpr –dc102 Date.java

(e) Create a subdirectory called prog04from whatever current

directory you are inmkdir prog04

(f) Move a file called assign02.java from your current directory

to an existing sub-directory called exam01mv assign02.java exam01

(g) Copy all *.java files from the /academic/cs2 directory to an existing

subdirectory of your current directory called prog04cp /academic/cs2/*.java prog04

(h) One command to find all files containing the string int in

your current directorygrep int *

(i) Delete a subdirectory of your current directory called prog04rmdir prog04

(j) Display the dates and protections of all files in your current

directory, one page at a timels -al

(k) Create a file, called dir, which contains the dates and

protections of all files in your current directory ls –al > dir

(l) Give an example of the alias commandalias lf ls -F

[1 pt each] 4. Explain, or give the vi command, or keystroke(s) to answer the following:

(a) Return to Command (or “travel”) mode from insert modeESC>

(b) While in Command (or “travel”) mode, move the cursor down

one linej

(d) While in Command (or “travel”) mode, delete the current linedd

(e) While in Command (or “travel”) mode, exit the file and save
all changesZZ

(f) While in Command (or “travel”) mode, begin inserting on the line

after the one the cursor is currently ono

(g) While in Command (or “travel”) mode, quit the file and do

not save the file:q!

5. Use the class definition at the right to answer the following questions. You will NOT need to modify the code at the right.

[3 pts] Give the output if the following segment of code was run:

Car acura = new Car();

System.out.println( acura.getColor() );

blue

[4 pts] Add line(s) below, if necessary, so the following code prints Yes!

Car CRV = new Car (2500,"silver");

Car Rav4 = new Car (2500,"silver");

CRV = Rav4

if (CRV == Rav4) {

System.out.println("Yes!");

} else {

System.out.println("No");

}

[4 pts] Add line(s) below, if necessary, so the following code prints No

No addl. code neccessary

Car CRV = new Car (2500,"silver");

Car Rav4 = new Car (2500,"silver");

if (CRV == Rav4) {

System.out.println("Yes!");

} else {

System.out.println("No");

}

[6 pts] Write the segment (NOT an entire program) of code which would declare and instantiate an array of n cars. You may assume that n is an integer and that you can use it in the code. All the new cars should be white and have initial mileage of 10.

Car[] carArray = new Car[n];

for (int i=0; i<n; i++) {

carArray[i] = new Car(10,"white");

}