Department of Computer Science

University of Illinois at Urbana-Champaign

Computer Science 101: Mid Term Exam II (60 minutes)

Name: NetID:

Lab Section: Date: November 1, 2007

No questions will be answered during this examination. If you do not understand a question, read it again. If you still do not understand it, make reasonable assumptions and write them down. (Points will be deducted if unreasonable assumptions are made.)

DO NOT CHEAT: Cheating includes not only copying from another person but also allowing someone to copy from you. Anyone who copies or allows someone to copy will receive a score of zero. So be defensive and protect your work.

This examination contains 11 pages including this page. Check that your copy is complete, and ask for a replacement if it is not. Do all your work on these pages. For your own protection, in case pages come apart, write your NetID at the TOP of each page before beginning work.

The number of points for a question is roughly proportional to the amount of time you may need for it. Don’t spend too much time on any one question.

Do not forget to sign the attendance list. If your exam is misplaced and you did not sign the attendance list then you will receive a zero score for the exam.

You may not use any electronic devices, book, notes or other references during this examination.

DO NOT WRITE IN THIS SPACE

Section	Possible Score	Deduction	Grader
1	6
2	5
3	5
4	5
5	8
6	8
7	5
8	7
9	6
10	6
11	8
12	10
13	6
14	14
15	14
16	12
Total	125
		Exam Scoreà

1. Answer the following questions by filling in the blanks.

a) When you use the Unix ls command to list the contents of a directory the output may not fit on one full terminal screen. Since the screen scrolls you may not see the first part of the output. Fill in the blank line to solve this problem:

ls -la ______ more

b) Fill in the blank to send the output from the ls command to the file “screen.txt”.

ls -la ______ screen.txt

2. Assume that you are in your home directory which contains the file lab9.c Write Unix commands to create a subdirectory named lab9 and next, without changing directories, copy the file named lab9.c located in your home directory into the lab9 directory (do not copy any other files).

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3. The following program is saved in a file named test.c,

#include <stdio.h>

#include <math.h>

void main(void)

{
double x;

printf("Enter a number:");

scanf("%lf", &x);

printf("sin(%lf) = %lf \n",x, sin(x));

}

Write a single command to compile the code in the file test.c, so that to run your program at the Unix prompt you would type:
testing
instead of a.out.

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4. Write a single Unix command to move the files named file1, file2, file3 located in your current directory into a subdirectory named dirname. You may assume that these three files are the only files located in your current directory and that dirname already exists.

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5. Which of the following code fragments assign the value 10 to each element of the array named Array ? Circle each correct answer. There may be more than one correct answer.

int Array[10][10];

int i,j;

for(i=0; i<10 ;i++)

for(j=0; j<10 ;j++)

Array[j][i] = 10;

int Array[10][10] = {10};

c)
int Array[10][10];

strcpy(Array,10);

int Array[10][10];
int i,j;

for(i=0; i<10 ; i++)

{
Array[0][i] = 10;

for(j=1; j<10 ; j++)

Array[j][i] = Array[j-1][i];

}

6. The following program compiles and runs without errors. Write the output of this program.

#include <stdio.h>

void main(void)
{

printf("%i ", 3/4);

printf("%i ", 3%4);

printf("%i ",3/4*4);

printf("%i ",3+3*3);

}

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7. The following program compiles and runs without errors. Write the output of this program:

#include <stdio.h>

void main(void)

{

int Array[3], Xarray[] = {1 , 2 , 3};

int i;

for(i=0 ; i<3 ; ++i)

{

Array[i] = i;
printf("%i ", Array[i]);

}

for(i=0 ; i<3 ; ++i)

printf("%i ", Xarray[i++]);

}

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8. There is an error on three different lines of code in the following program. Write the corrected lines in the blanks provided. Only three lines need be rewritten. There is one syntax error, one run time error and one logical error.

The program below should read 3 integers, compute and display the average of the 3 integers.
For example, if the 3 integers were 2, 3 and 5 then the program would print the average as 3.33.

#include <stdio.h>

void main(void)

{
int i, sum=0; _____________________________

int Array(3); _____________________________

for(i=0 ; i< 3 ; ++i) _____________________________

scanf("%i", Array[i]); _____________________________

for(i=0 ; i< 3 ; ++i) _____________________________

sum += Array[i]; _____________________________

printf("%.2f \n",sum/3); _____________________________

}

9. The following C program compiles and runs without errors.

Write the output of this program when it is executed.

#include <stdio.h>

void main(void)

{

int i = 1, n = 3, sum1 = 0, sum2 = 0,sum3 = 0;

while(i <= n)

{

sum1 = sum1 + i;

i = i + 1;

}

printf("%i %i \n",i,sum1);

for(i = 1; i <= n; i = i+1)

sum2 = sum2 + i;

printf("%i %i \n",i,sum2);

i = 5;
do{

sum3 = sum3 + i;

i = i + 1;

}while(i <= n);

printf("%i %i \n",i,sum3);

}

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DO NOT WRITE IN THIS SPACE

Section

Possible Score

Deduction

Grader