paper 2 Flashcards
what is meant by decomposition
breaking a complex problem down into smaller problems and solving them individually
what is meant by abstraction
picking out the important bits of the information and leaving out the specific details that don’t matter
why is using algorithmic thinking useful when solving a problem
that algorithm could then be reused and adapted to solve similar problems in the future
what is meant by algorithmic thinking
a logical way of getting from a problem to the solution
define integer
whole number
define real
decimal numbers
define boolean
can only take one of two values usually TRUE or FALSE
define character
a single, letter, number, or symbol
define string
a collection of characters
what does casting mean
changes the data type
explain what int() does
converts the string 1 to the number 1
explain what float() does
converts the integer 1 to the float 1.0
explain what str() does
converts boolean true to the string true
explain what ASC() does
converts character b to ASCII number 98
explain what CHR() does
converts number 98 to ASCII letter b
how does == differ from =
= assignment opperator, == comparison opperator
what does != do
is not equal to
what does ** do
multiplies a number to the power of a number
what is meant by a constant
assigned to a data value and cannot be changed
what is meant by a variable
assigned to a data value and can be changed
define string concatenation and give an example of it being used
joining together strings end-to-end
x = “Python is “
y = “awesome”
z = x + y
print(z)
explain what x.upper does
changes all characters in string x to upper case
explain what x.lower does
changes all characters in string x to lower case
explain what x.length does
returns the number of characters in string x
explain what x.subString(a,b) does
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
why is binary used in computers
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
what are the units in order size
bit nibble byte kilobyte megabyte gigabyte terabyte petabyte
convert 240 into binary
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
convert 148 into hexadecimal
148%16 =9 remainder 4
148 = 94
convert 00111000 into denary
128-64-32-16-8-4-2-1
0- 0- 1- 1- 1-0-0-0
00111000 = 32+16+8 = 56
convert 101011 into hexadecimal
split byte into nibbles 4-2-1 4-2-1 1-0-1 0-1-1 4+1 = 5 2+1=3 101011=53
convert 4A into denary
4*16 =64 10=a
64+10=74
4A = 74
convert D9 into binary
D=13 = 1101 9= 1001 D9 = 11011001
add the binary numbers 01011101 and 00110010
0 1 0 1 1 1 0 1
0 0 1 1 0 0 1 0
——————-
1 0 0 0 1 1 1 1
what is an overflow error
when a number has too many bits
what effect do left and right shifts have on binary numbers
for every place shifted left the number doubles
for every place shifted right the number halves
give three reasons why programmers prefer hexadecimal over binary and denary
simpler to remember large numbers in hex
less chance of input errors
easier to convert between binary and hex
what is the definition of a character set
a collection of characters that the computer recognises from their binary representation
give the four types of characters that are included in the character set
letters
symbols
numbers
special characters which do commands (space)
what are the three main character sets
ASCII - most commonly used character set and can represent 128 different characters
Extended ASCII - 256 characters
Unicode - every possible character
how many bits does it take to represent each character in the main character set
ASCII - 7 bits A-65 a-97
Extended ASCII - 8 bits
Unicode - 16-bit and 32-bit
What is iteration?
‘iteration’ is repeating the same code more than once (looping).
Iteration is one of three main constructs in programming
What type of programming construct is demonstrated by the following pseudocode:
for i=0 to 7
print(i)
next i
This is an example of iteration
How many times would the following pseudocode print?
for i=0 to 7
print(i)
next i
8 times - 0 1 2 3 4 5 6 7
What would the following pseudocode do?
for i=0 to 7
print(i)
next i
it would print the numbers 0 1 2 3 4 5 6 7
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
This is an example of selection
What does the following pseudocode do?
while answer != ”computer”
answer=input(“What is the password?”)
endwhile
repeatedly asks the user to input the password until they enter “computer”
What is sequence?
‘sequence’ is about the ordering of the steps in an algorithm.
sequence is one of 3 main constructs in programming.
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?”)
sequence
