1.2.4 data storage

Question 1

binary

Answer 1

base 2

range: 00000000 - 11111111

Question 2

denary

Answer 2

base 10

range: 0 - 255

Question 3

hexadecimal

Answer 3

base 16
this includes: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
range: 00 - FF

Question 4

MSB and LSB

Answer 4

most significant bit = bit 7

least significant bit = bit 0

Question 5

why is hexadecimal used to represent numbers instead of binary?

Answer 5

they take up less space and they are easy to spot errors with

Question 6

binary to hex

Answer 6

split the 8 digit binary into two nibbles
convert the two nibbles to denary
convert both denary numbers into hexadecimal

Question 7

hex to binary

Answer 7

split the hex digit into two
convert both hex digits to denary
convert both denary numbers into nibbles
put the two nibbles together to make a byte

Question 8

hex to denary

Answer 8

split the two digits
convert each digit into a nibble
put the nibbles together to form a byte
convert the byte to denary

Question 9

denary to hex

Answer 9

convert denary into binary
split into two nibbles
convert each nibble into hex
put the two digits together

Question 10

overflow errors

Answer 10

when adding two binary numbers we can end up with an extra digit that doesn’t fit. this is called an overflow error
this might make the program crash

Question 11

left binary shifts

Answer 11

1 shift left = X2
2 shifts left = X4
3 shifts left = X8
you may get overflows with left binary shifts

Question 12

right binary shifts

Answer 12

1 shift right = ÷2
2 shifts right = ÷4
3 shifts right = ÷8
you may get an underflow with right binary shifts

Question 13

characters

Answer 13

each character is represented by a unique binary number
a character set is the possible characters that can be represented by a computer system
well known character sets include: ASCII, extended ASCII and Unicode

Question 14

ASCII

Answer 14

a 7 bit character set with 128 characters
it is stored as a byte (8 bits) but only uses 7 bits
the 8th bit can be used for other sets such as the extended ASCII.

Question 15

extended ASCII

Answer 15

an 8 bit character set with 256 characters

this is used for languages such as Spanish or French

Question 16

unicode

Answer 16

Unicode was developed to code for every language in the world
it uses two bytes which gives us 2^16 character possibilities (65,536)

Question 17

images

Answer 17

images can be stored in binary as bitmap or vectors
bitmap pictures: made from coloured squares called pixels
vector pictures: drawn by following a set of mathematical instructions

Question 18

metadata

Answer 18

metadata is data about data

It tells us the file type, size, location, date and time etc.

Question 19

bitmap images

Answer 19

each pixel of a bitmap is stored in binary
each pixel has a specific colour, represented by a specific code
the number of bits required for each pixel depends on the number of colours required
the number of colours can be calculated as 2^n - where n is the number of bits for each pixel
the number of bits determines the range of colours, known as the colour depth
colour depth is the range of colours available
image size = height X width X colour depth

Question 20

resolution

Answer 20

resolution is the number of pixels per image

the greater the colour depth and resolution, the more realistic colours and the larger the file size of the image