data types

Question 1

character set

Answer 1

the mapping of a collection of characters to specific bit sequences or codes

Question 2

all data types are held in the computer as…

Answer 2

binary

Question 3

character

Answer 3

a letter, number or special character typically represented in ASCII

Question 4

max and min values represented by n bits in binary

Answer 4

min =0
max = 2^n -1
(so total characters represented 2^n)

Question 5

why is hex used rather than binary

Answer 5

less likely to make mistakes
easier to remember
simpler

Question 6

define bit

Answer 6

fundamental unit of information in the form of either a single 0 or 1.

Question 7

increasing order of numbers 2^10, 2^20….2^80

Answer 7

kibi (Ki), mebi (Mi), gibi (Gi), Tebi (Ti), Pebi (Pi), Exbi (Ei), Zebi (Zi), Yobi (Yi)

Question 8

increasing order of numbers 10^3, 10^6…10^24

Answer 8

Kilo (K), Mega (M), Giga (G), Tera (T), Peta (P), Exa (E), Zetta (Z), Yotta (Y)

Question 9

ASCII- american standard code for information interchange

Answer 9

historically the standard code for representing letters on keyboard. first 32 = non printing. 7 bits = 128 characters. developed to 8 bits (compatible by just adding a 0) so 128 more characters for symbols

Question 10

UNICODE

Answer 10

1980s, several incompatible coding systems for different languages, difficulty because multilingual data increasingly used, so UTF-16, 65536 characters for different languages e.g. Latin, Greek, Arabic. First 128 same as ASCII so compatible. then UTF-32 inc chinese and japanese.
But now each character- 4 bytes rather than 2 so inc file sizes and transmission times.

Question 11

overflow

Answer 11

when most significant bit has a carry, requiring an extra bit. when when the largest number a register can hold has exceeded its max word size

Question 12

why is sign and magnitude bad for arithmetic

Answer 12

can’t just add binary digits, difficult for representing in hardware

Question 13

range using two’s complement

Answer 13

-2^(n-1) ….. 2^(n-1) -1

Question 14

fixed point accuracy

Answer 14

less accurate, some fractions can’t be represented at all and truncating to fractional places means less accurate and rounding errors.
range is limited by fractional part: can have larger, less acc numbers or smaller more acc numbers

Question 15

floating point acc

Answer 15

much larger numbers and more accurate.

mantissa determines precision and exponent determines range.

Question 16

normalisation

Answer 16

process of moving the binary point to provide max level of precision for a given number of bits

Question 17

normalised binary mantissa

Answer 17

lies between half and one or minus half and minus one for negative

Question 18

logical shift instructions

Answer 18

all the bits move left or right

Question 19

why is logical shift useful

Answer 19

for examining LSB/MSB: carry bit can then be tested and a conditional branch executed

Question 20

logical shift right explain..

Answer 20

LSB shifted to carry bit and zero moves into MSB to occupy vacated space

Question 21

arithmetic shift instructions

Answer 21

all bits move left or right except sign bit, which is taken into account and remains the same

Question 22

arithmetic shift left explain..

Answer 22

shift bypasses the sign bit so the MSB remains the same but all other bits shift left and second bit from left is now in carry bit

Question 23

effect of arithmetic shift left

Answer 23

multiplying by 2

Question 24

effect of arithmetic shift right

Answer 24

dividing by 2

Question 25

how can you multiply two binary numbers

Answer 25

arithmetic shifts and addition

Question 26

multiply 9 x 5 using arithmetic shifts?

Answer 26

9x1 ADD 9x4 via 2 left shifts

Question 27

circular shifts/rotate shifts are useful for

Answer 27

shifts in multiple bytes

Question 28

circular shift right explain…

Answer 28

LSB value moved to carry bit

Question 29

define bitwise operations

Answer 29

similar to boolean logic operations but they work on individual bits in a byte rather than whole codes or characters

Question 30

define masks

Answer 30

bit patterns that have been defined by a programmer, allowing specific bits in a piece of data to be altered or tested

Question 31

masks: how to reset/turn off a bit to 0

Answer 31

can’t use OR, use AND instead

Question 32

masks: how to turn on a specific bit

Answer 32

can use OR

Question 33

masks: how to check a specific bit

Answer 33

set all other bits to 0 using ‘AND 0’ as operation and mask except for the specific bit: 1

Question 34

masks: how to toggle bits- turn bits on and off at the same time

Answer 34

use ‘XOR’ operation and 0 for the ones to remain the same and 1 for the ones to toggle