1. Data storage

Question 1

What are Bits?

Answer 1

Binary digit that has two values.

Question 2

What does a bit patterns represent?

Answer 2

Numbers, text, images, sound and truth values

Question 3

Boolean operation?

Answer 3

Are operations on truth values

Question 4

Boolean operators:

Answer 4

And
Or
XOR
Not

Question 5

What is a gate?

Answer 5

A gate is a device that computes a Boolean operation.

Question 6

What does those Boolean numbers represent?

AND: x= 1, y= 0
AND: x=1, y= 1
OR : x= 0, y= 1
OR: x= 1, y= 1
XOR: x= 1,y= 1
NOT x: x= 0

Answer 6

0
1
1
1
0
1

Question 7

What is a Hexadecimal notation?

Answer 7

Is used as a base and has four bit pattern that represents one number between 0 and 9 and six different letters.

Question 8

What are the letters in a Hexadecimal notation and what they represent?

Answer 8

A-10 , B-11, C-12, D-13, E-14, F-15

Question 9

What does this bit patterns represent?

Answer 9

0000/ 0
0001/ 1
0010/ 2
0011/ 3
0100/ 4
0101/ 5
0110/ 6
0111/ 7
1000/ 8
1100/ 9
1010/A
1011/B
1100/C
1101/D
1110/E
1111/F

Question 10

Main memory (RAM) premiär minne.

Answer 10

Consist of large number of circuits each capable of storing a single bit.

Question 11

How are main memory organized?

Answer 11

It is organized in units called memory cells, with a typical size of 8bits

Question 12

What are bytes?

Answer 12

Bytes are a group of 8 bits

Question 13

What do you assign memory cells?

Answer 13

Memory cells are assigned numbers (starting with 0) which are called addresses

Question 14

What are addresses for?

Answer 14

The addresses works as a map, when we need information we can access it quickly by going to the address of a cell where the cell itself is implicit. They are stored (implicit) in order so we can access it quickly

Question 15

Types of Mass storage?

Answer 15

-The magnetic disks such as HDD’s
-Optical discs: CD’s DVD’s and blue rays
- Flash memory, solid state drive: SSD and secure digital: SD

Question 16

what are the advantages of mass storage over main memory?

Answer 16

• less volatile, they are not dependent on currents.
• lower costs
• larger storage capacities.

Question 17

how do you represent text?

Answer 17

character encodings - mapping bit patterns to characters. mellan en bit mönster och ett tecken.

Question 18

what is the first Standard code?

Answer 18

ASCII is the first (American Standard Code for Information Interchange) 7-bits: 128 characters.

Question 19

How are ASCII characters represented?

Answer 19

they are represented in zeros and ones which are assigned to characters. the first bunch are only commands and when we come to 0100000 it starts with characters that we can print out. (show on the screen)

Question 20

why is there numbers as characters?

Answer 20

In ASCII, zero (0) for example is a character and not a number so it doesn’t have a numerical value. its represented as 0110000.

Question 21

the problem with ASCII?

Answer 21

ASCII doesn’t have the characters that are not in the English language, so there is a non standardized ASCII which has 8-bits that can represent 256 characters instead of 7-bits

Question 22

there is problems with using the different standards:

Answer 22

• First it becomes a not standard, as in there are too many.
• Second the machines built with one standard cant be read correctly by another machine with a different standard

Question 23

How did we solve it?

Answer 23

To solve the standard problem we introduced Unicode.
- Unicode is able to represent all characters in all languages.
- The first 128 is the same as ASCII.
- UTF-8 is (Unicode transformation Format 8-bit) it uses 8 or more bits per character.
- the ASCII characters can then be represented with 8-bits but for example öåä needs 16-bits to be represented in UTF-8.
- there can be 24-bits and 32-bits and so on.
- Although not everyone uses it and we can see it till today that sometimes other people cant read or receive the special characters.

Question 24

How do we represent images?

Answer 24

we do it in two steps:
- the first is to use a grid-pattern over the image and each square represent a pixel (picture element) the resolution is how many pixels we have.

Question 25

How do you translate it into zeros and ones?

Answer 25

Pixel by pixel we can represent them by 0 is white and 1 is black each pixel has a a bit.

Question 26

how do we do with multiple colors?

Answer 26

we need to more than 1-bit per pixel.
Color depth is how many bits we save in one pixel. Color/bit depth (bits per pixel. For example 24-bits per pixel and so on.
- The standard is RGB which is 24 bits per pixel. We do that by having 8-bits to represents how much red, and 8-bits for how much green and 8-bits for how much blue is in one pixel. Total is 24-bits. we can have any color by mixing those 24-bits. We get yellow by having a lot of Red and Green and non Blue. Its not the same as printed colors.

Question 27

How do we represent sound?

Answer 27

Its very similar to image.
- We do that by sample rate and sample depth.

Question 28

what is sample rates?

Answer 28

They are how many samples we play per time unit. the CD for example has 44100 samples per second. and this is the same as resolution of an image. the higher the number the better we can represent it.

Question 29

Sample depth?

Answer 29

It is the same as color depth, which means how many bits per sample. CD uses 16-bits per channel. CD’s stands for stereo which means we have two channels and so it can represent 32-bits per sample.

Question 30

How do we represent integers (Heltal)

Answer 30

• The normal decimal number (base 10) such as 10437 where: the 7 means 7 and the 3 means 30 (310) and the 4 means 400(4100) and and the 0 means 0 (01000) and the last 1 means 10000 (110000) so on.
• Bit patter (base 2)
  such as 10100101 from right to left: the 1 is one and the second bit 0 means 0(02) and the third bit 1 means 4 (14) and so on. so for each time we go to the left we increase with 2.

Question 31

How do we represent the number 190?

Answer 31

10111110

1 - 0 - 1 - 1 - 1 - 1 - 1 - 0
128 - 64 - 32 - 16 - 8 - 4 - 2 - 1
128 - 0 - 32 - 16 - 8 - 4 - 2 - 0

Question 32

storing integers

Answer 32

many standards to store integers both positives and negatives.

Question 33

Unsigned

Answer 33

means we have 4-bits patterns and we do it normally as in to the base of 2.

Question 34

signed magnitude

Answer 34

is a way to represent negatives where we put a 1 in the most significant such as 1100 which means negative -4 and 1010 means negative -2 and so on.
- a problem is that we have two zeros. 0000 = +0 and 1000 = -0.

Question 35

two’s complement

Answer 35

is the standard to represent negatives numbers where the most significant is the highest negative number we can get from a 4-bits pattern.
such as 1000 which means negative -8.
and 1100 means -8 + 4 + 0 + 0 = -4

Question 36

Excess-k or (Excess-8)

Answer 36

is where we start from 0000 and it represent a negative -8 and we add 1 as we go from right to left so 0001 is -7 and 1001 is 1 and 1110 is 6

Question 37

Overflow

Answer 37

Overflow is when a number is too large or too small to be stores in the available number of bits.
example: if we want to represent 8 in the two’s complement method what do we do? the highest number is 7 and the lowest is -8.
which means we need to add more bits

Question 38

Truncation

Answer 38

Happens when precision is lost because of limited number of available bits.