Lecture 8

Question 1

Rightmost bit is

Answer 1

the least significant LSB or low-order bit

Question 2

leftmost bit is

Answer 2

the most significant bit (MSB) or high-order bit

Question 3

byte is collection of

Answer 3

8 bits

Question 4

a bit is

Answer 4

a single binary digit

Question 5

memory

Answer 5

is just an array of bytes

Question 6

The binary number 01100100 represents

Answer 6

100 ( 2^2 + 2^5 + 2^6)

Question 7

two’s complement notation

Answer 7

handling of negative numbers in computers

Question 8

If the leftmost number is 1

Answer 8

then it can be represented as a negative number

Question 9

11111111 represents

Answer 9

-1

Question 10

if w1 and w2 are both defined as short int , and w1 is set equal to 25 and
w2 is set equal to 77, then the C statement w3 = w1 & w2; What is the value assigned to w3?

Answer 10

9
w1 0000000000011001 = 25
&
w2 0000000001001101 = 77
———————————-
w3 0000000000001001 = 9

It compares the value in w1 and w3

Question 11

Bitwise ANDis frequently used for

Answer 11

MASKING operations; where you use a specific binary value (like 3) to selectively “mask” certain bits of another number (here, w1), effectively zeroing out the bits that don’t correspond to 1 in the mask

Question 12

w1 is 11001010 (an 8-bit binary number), and 3 is 00000011.

Performing w1 & 3 will look

Answer 12

w1: 11001010
3 : 00000011
—————-
w3: 00000010

Question 13

Is word &= 15; equivalent to word = word & 15; ?

Answer 13

yes

Question 14

What is the equivalent to Stress = Stress & 100

Answer 14

Stress &= 100;

Question 15

Is the bitwise AND operator & the same as the logical AND operator &&?

Answer 15

NO

Question 16

When dealing with 32- of 64-bit computers, which notation is most often used

Answer 16

Hexadecimal

Question 17

the octal constant of 0177 represents what decimal value

Answer 17

=127 (1 * 64 + 7 * 8 + 7)

Question 18

to display an integer in octal?

Answer 18

printf( %o)

Question 19

Convert the decimal number 2345 into hexadecimal

Answer 19

0x929

Question 20

Convert the decimal number 512 into octal.

Answer 20

1000 (in octal).

Question 21

Convert Hexadecimal 0x1A3 to Decimal

Answer 21

419

Question 22

Convert Octal 725 to Decimal

Answer 22

469

Question 23

Base of Hexidecimal

Answer 23

16

Question 24

Base of Octal

Answer 24

8

Question 25

So, if w1 is an unsigned int equal to octal 0431 and w2 is an unsigned int equal to octal 0152 , then a bitwise OR of w1 and w2 would produce what result

Answer 25

w1 ... 100 011 001 0431 | (OR) w2 ... 001 101 010 0152 ---------------------------- ... 101 111 011 0573 which equals 379 in decimal

Question 26

What is this bitwise operator called: If either bit is a 1—but not both—the corresponding bit of the result is a 1; otherwise it is a 0.

Answer 26

XOR operator ^

Question 27

If w1 and w2 were set equal to octal 0536 and octal 0266 , respectively, then the result of w1 Exclusive-ORed with w2 would be?

Answer 27

octal 0750 w1 ... 101 011 110 0536 ^(XOR) w2 ... 010 110 110 0266 -------------------------- ... 111 101 000 0750

Question 28

How do you use XOR to swap two integers without using a temporary: temp = i1; i1 = i2; i2 = temp;

Answer 28

i1 ^= i2; i2 ^= i1; i1 ^= i2;

Question 28

What does this complement operator ~ do?

Answer 28

flip the bits of its operand

Question 29

If w1 is a short int that is 16 bits long, and is set equal to octal 0122457 , then taking the ones complement of this value produces?

Answer 29

w1 1 010 010 100 101 111 0122457 ~w1 0 101 101 011 010 000 0055320

Question 29

What will be the result of the following C code snippet, and explain the steps involved? int w1 = 5; // Initial value w1 <<= 2; // Left shift w1 by 2 bits

Answer 29

w1 now holds the value 20 Original: 0101 (5 in decimal) Shifted: 010100 (after shifting left by 2 bits) 010100 = 20

Question 30

If w1 is an unsigned int , which is represented in 32 bits, and w1 is set equal to hexadecimal F777EE22 , then shifting w1 one place to the right with the statement w1 >>= 1; sets w1 equal to?

Answer 30

7BBBF711 w1 1111 0111 0111 0111 1110 1110 0010 0010 F777EE22 w1 >> 1 0111 1011 1011 1011 1111 0111 0001 0001 7BBBF711

Question 31

how to access UNIX box

Answer 31

ssh -Y

Question 32

What is a GUI

Answer 32

a window manager: gnome, KDE, etc. Manages the invocation of processes via mouse and keyboard

Question 33

What files are commonly used to configure a user’s shell environment in Linux?

Answer 33

.bashrc, .profile, and .login are commonly used configuration files

Question 34

What command can you use to view all current environment variables in a Bash session?

Answer 34

Use set, env, or printenv to view environment variables.

Question 35

How can you create your own environment variables in Bash?

Answer 35

Use export VAR=value to set your own environment variables.

Question 35

What happens to environment variables defined in a Bash session if not exported?

Answer 35

They only exist in the shell where they are defined and do not persist after closing the session.

Question 36

What occurs when Bash executes a command?

Answer 36

Bash forks a copy of itself and then uses exec to run the new command

Question 36

What is the significance of the $PATH variable?

Answer 36

The $PATH variable specifies the directories where executable programs are located, allowing you to run commands without specifying their full paths.

Question 37

How can you create aliases to simplify command usage in Bash?

Answer 37

Use the alias command, e.g., alias h=history or alias rm=rm -i to create shortcuts.

Question 37

What is the benefit of using aliases like alias rm=rm -i?

Answer 37

It prompts before deleting files, helping to prevent accidental file deletions.

Question 38

How can you bypass an alias in Bash?

Answer 38

Use a backslash before the command, e.g., \rm -f to ignore the alias and use the original command.

Question 39

In which standard directories do most commands reside in a Linux system?

Answer 39

Most commands are located in /bin, /usr/bin, /usr/local/bin, and /opt/X11/bin.

Question 40

What wildcards can you use in the shell for pattern matching?

Answer 40

Use * (matches any number of characters) and ? (matches a single character) as wildcards in the shell.

Question 40

How can you find the path to a specific command binary or shell script?

Answer 40

Use which or whereis to locate the command binary or shell script.

Question 40

How can you search for the end of a line in Vim?

Answer 40

Use $ to search for the end of a line.

Question 41

What types of files can commands be, apart from binary executables?

Answer 41

Commands can also be shell programs, Python scripts, Perl scripts, and similar types of scripts.

Question 42

What command can you use to find the location of a binary, header, or source file?

Answer 42

Use the locate command to find the location of files.

Question 43

How can you access your recent commands in the terminal?

Answer 43

Use the history command, the up-arrow key, or the !command or !number syntax to access commands from the history buffer.

Question 44

What wildcard does Vim use to represent any single character?

Answer 44

In Vim, the . wildcard represents any single character.

Question 45

How can you search for the beginning of a line in Vim?

Answer 45

Use ^ to search for the beginning of a line.

Question 46

What does the Vim command :1, /ending/ do?

Answer 46

It searches from the first line to the line containing the word "ending".

Question 47

What does the Vim command :1,$s/me/mine/g accomplish?

Answer 47

It substitutes every occurrence of "me" with "mine" in the entire file (from the first line to the last).

Question 48

What is the effect of the Vim command :1,$s/^Student Number/SNUM/?

Answer 48

It replaces "Student Number" at the beginning of any line with "SNUM" throughout the entire file.