paper 2

Question 1

what is meant by decomposition

Answer 1

breaking a complex problem down into smaller problems and solving them individually

Question 2

what is meant by abstraction

Answer 2

picking out the important bits of the information and leaving out the specific details that don’t matter

Question 3

why is using algorithmic thinking useful when solving a problem

Answer 3

that algorithm could then be reused and adapted to solve similar problems in the future

Question 4

what is meant by algorithmic thinking

Answer 4

a logical way of getting from a problem to the solution

Question 5

define integer

Answer 5

whole number

Question 6

define real

Answer 6

decimal numbers

Question 7

define boolean

Answer 7

can only take one of two values usually TRUE or FALSE

Question 8

define character

Answer 8

a single, letter, number, or symbol

Question 9

define string

Answer 9

a collection of characters

Question 10

what does casting mean

Answer 10

changes the data type

Question 11

explain what int() does

Answer 11

converts the string 1 to the number 1

Question 12

explain what float() does

Answer 12

converts the integer 1 to the float 1.0

Question 13

explain what str() does

Answer 13

converts boolean true to the string true

Question 14

explain what ASC() does

Answer 14

converts character b to ASCII number 98

Question 15

explain what CHR() does

Answer 15

converts number 98 to ASCII letter b

Question 16

how does == differ from =

Answer 16

= assignment opperator, == comparison opperator

Question 17

what does != do

Answer 17

is not equal to

Question 18

what does ** do

Answer 18

multiplies a number to the power of a number

Question 19

what is meant by a constant

Answer 19

assigned to a data value and cannot be changed

Question 20

what is meant by a variable

Answer 20

assigned to a data value and can be changed

Question 21

define string concatenation and give an example of it being used

Answer 21

joining together strings end-to-end

x = “Python is “
y = “awesome”
z = x + y
print(z)

Question 22

explain what x.upper does

Answer 22

changes all characters in string x to upper case

Question 23

explain what x.lower does

Answer 23

changes all characters in string x to lower case

Question 24

explain what x.length does

Answer 24

returns the number of characters in string x

Question 25

explain what x.subString(a,b) does

Answer 25

extracts a string at position a and length b from string x
x = hello
 x.substring(3,2) =lo
0 1 2 3 4
h e l   l  o

Question 26

why is binary used in computers

Answer 26

computers use electronic circuits that function as switches and can be turned on and off
0 represents on
all data must be converted into binary to be processed

Question 27

what are the units in order size

Answer 27

bit 
nibble
byte
kilobyte
megabyte
gigabyte
terabyte
petabyte

Question 28

convert 240 into binary

Answer 28

128 - 64 - 32 - 16 - 8 - 4 - 2 - 1 [240- 128=112]

1 1 1 1 0 0 0 0 [112-64 = 48] [48-32=16] [16-16=0] [0-8=-8]​ 240 =11110000

Question 29

convert 148 into hexadecimal

Answer 29

148%16 =9 remainder 4

148 = 94

Question 30

convert 00111000 into denary

Answer 30

128-64-32-16-8-4-2-1
0- 0- 1- 1- 1-0-0-0
00111000 = 32+16+8 = 56

Question 31

convert 101011 into hexadecimal

Answer 31

split byte into nibbles 
4-2-1        4-2-1
1-0-1         0-1-1
4+1 = 5     2+1=3
101011=53

Question 32

convert 4A into denary

Answer 32

4*16 =64 10=a
64+10=74
4A = 74

Question 33

convert D9 into binary

Answer 33

D=13 = 1101
9= 1001
D9 = 11011001

Question 34

add the binary numbers 01011101 and 00110010

Answer 34

0 1 0 1 1 1 0 1
0 0 1 1 0 0 1 0
——————-
1 0 0 0 1 1 1 1

Question 35

what is an overflow error

Answer 35

when a number has too many bits

Question 36

what effect do left and right shifts have on binary numbers

Answer 36

for every place shifted left the number doubles

for every place shifted right the number halves

Question 37

give three reasons why programmers prefer hexadecimal over binary and denary

Answer 37

simpler to remember large numbers in hex
less chance of input errors
easier to convert between binary and hex

Question 38

what is the definition of a character set

Answer 38

a collection of characters that the computer recognises from their binary representation

Question 39

give the four types of characters that are included in the character set

Answer 39

letters
symbols
numbers
special characters which do commands (space)

Question 40

what are the three main character sets

Answer 40

ASCII - most commonly used character set and can represent 128 different characters
Extended ASCII - 256 characters
Unicode - every possible character

Question 41

how many bits does it take to represent each character in the main character set

Answer 41

ASCII - 7 bits A-65 a-97
Extended ASCII - 8 bits
Unicode - 16-bit and 32-bit

Question 42

What is iteration?

Answer 42

‘iteration’ is repeating the same code more than once (looping).

Iteration is one of three main constructs in programming

Question 43

What type of programming construct is demonstrated by the following pseudocode:

for i=0 to 7
print(i)
next i

Answer 43

This is an example of iteration

Question 44

How many times would the following pseudocode print?

for i=0 to 7
print(i)
next i

Answer 44

8 times - 0 1 2 3 4 5 6 7

Question 45

What would the following pseudocode do?

for i=0 to 7
print(i)
next i

Answer 45

it would print the numbers 0 1 2 3 4 5 6 7

Question 46

Which programming construct is shown by the following pseudocode?

if entry == ”a” then
print(“You selected A”)
elseif entry == ”b” then
print(“You selected B”)
else
print(“Unrecognised selection”)
endif

Answer 46

This is an example of selection

Question 47

What does the following pseudocode do?

while answer != ”computer”
answer=input(“What is the password?”)
endwhile

Answer 47

repeatedly asks the user to input the password until they enter “computer”

Question 48

What is sequence?

Answer 48

‘sequence’ is about the ordering of the steps in an algorithm.

sequence is one of 3 main constructs in programming.

Question 49

Which programming construct is shown by the following pseudocode?

print(“Welcome to my program”)
username = input(“What is your username?”)
password = input(“What is your password?”)

Answer 49

sequence