Bits and Bytes

Question 1

What is a byte?

Answer 1

It is a group of 8 bits that can be individually addressable.

Question 2

What is a bit?

Answer 2

Holds 0 or 1

Question 3

What is a word?

Answer 3

● It is a group of 4 bytes (32 bit architecture) or
● It is a group of 8 bytes (64 bit architectures)
● The address of a word is aligned to either 4 or 8 bytes respectively (multiple of 4 or 8 bytes).

Question 4

What is memory mapped I/O?

Answer 4

When device registers are mapped to
memory.

A bit can represent the state of the device.

Question 5

What are 3 examples of Character Encodings broken question

Question 6

Who created Extended Binary Coded Decimal Interchange Format?

Answer 6

● It was created by IBM in the 1960s
● No longer in use except in some IBM
mainframes

Question 7

What does ASCII stand for?

Answer 7

American Standard Code for Information
Exchange

Question 8

How many bits/values does ASCII use?

Answer 8

It uses 7 bits or 128 values

Question 9

What does ascii encode?

Answer 9

The English alphabet

Question 10

How many bits does Unicode use?

Answer 10

16 bits (2 bytes)

Question 11

What does unicode encode?

Answer 11

Languages from all around the world

Question 12

What languages use unicode internally for strings?

Answer 12

Java and C#

Question 13

How does Pascal represent strings?

Answer 13

The first byte is the length of the string

Question 14

How do you perform math in binary? (Addition, Subtraction, Multiplication, Division)

Answer 14

Same as decimal, just with binary digits

Question 15

What ways are Negative Binary numbers represented?

Answer 15

● Sign and Magnitude
● 1-complement
● 2-complement

Question 16

How does Sign and Magnitude
Representation work?

What is the value of 10000101?

Answer 16

1 bit for sign, 1 means negative, rest of the bits for absolute value.

Value of 10000101 is -5. first one means negative

Question 17

How does 1-Complement work?

What is the value of 11111110

Answer 17

Negative numbers are obtained by inverting all bits.

11111110 is -1. invert all 00000001, neg of that

Question 18

How does 2-Complement work?

What is the value of 5 in binary for 2-Com?

Answer 18

Negative numbers are obtained by
subtracting 1 from the positive number and inverting the result.

11111011

Question 19

Why is 2-Complements widely used?

Answer 19

because the same piece of hardware used
for positive numbers can be used for negative numbers:

Question 20

How does right shift&raquo_space; change for signed vs unsigned ints?

Answer 20

if signed and the int is negative, 1s will be added, this is called “signed extension”

Question 21

What do bitwise operations |, &, ^, ~ all do?

Answer 21

bitwise or, and, xor, not on each bit

Question 22

How to check if bit x is set?

Answer 22

shift bit 1 x units to the left. Use & on shifted bit and comparing int.

Then take result and shift x right, if equal to 1 return true, found set bit

Question 23

How to set bit?

Answer 23

Use | with desired bit

Question 24

How does floating point representation work?

Answer 24

Store both the exponent and mantissa
ex” 1.101x2^-010

Question 25

What are the two representations for real numbers?

Answer 25

Fixed point numbers and
Floating Point Numbers:

Question 26

How do fixed point numbers work for real numbers?

Answer 26

Fixed number of bits for both integer and mantissa.
N.M – N bits for integer part and M bits for mantissa.
Example: 16 bit real number N =8 bits, M = 8 bits
Problem: Range of numbers is small. N=8 bits can
represent therange -128 to +127
+127=01111111=+127
-128=~(10000000-1)=-~(01111111)=10000000=-128

Question 27

How do floating point numbers work for real numbers?

Answer 27

The bits allocated for integer part and mantissa is variable.
Example= N.M where N+M =16bits
● Decimal point moves. Improved range but complex

Question 28

What is the most common Floating Point Representation standard?

Answer 28

IEEE-754 standard

Question 29

What order is Little Endian?

Answer 29

Least significant byte of the integer
is in the lowest memory location.

Question 30

What order is Big Endian?

Answer 30

Most significant byte of the integer is
in the lowest memory location

Question 32

How can you test if Little Endian?

Answer 32

cast little int pointer to char, if value of char is int value then little endian.

Question 33

What is the size of integers floats and pointers and doubles in 32 bit architecture?

Answer 33

4 bytes for everything but doubles are 8

Question 34

what is the size of pointers in 64 bit architecture?

Answer 34

8 bytes

Question 35

struct {
char ch1;
int r;
char ch2;
char * a;
} x;

What is the size of the above structure in 64 bit architecture

Answer 35

24 bytes