paper 1

Question 1

examples of analysis stage work during software dev

Answer 1

• problem definition
• list of objectives
• data model
• interviews
• questionnaires
• research existing solutions
• acceptable limitations / constraints

Question 2

why use named constants

Answer 2

• makes clear what the value held by the constant actually is / used for
• if the constant’s value would need to be changed, it only needs to be changed in one place
• improves readability of the code

Question 3

purpose of a hierarchy chart

Answer 3

• represent the structure of the program
• to aid decomposition of a problem

Question 4

differences between local and global variables

Answer 4

• global variables accessible to all parts of the program / have global scope
• global variables declared in main program block
• local variables declared in subroutine
• local variables accessible only in program block/subroutine they were declared in

Question 5

why use local variables

Answer 5

• makes a subroutine self-contained
• easier to re-use subroutine in another program
• releases storage when subroutine terminates

Question 6

decomposition

Answer 6

breaking a problem into a number of sub-problems that are easier to understand, program and maintain

Question 7

automation

Answer 7

models are put into action to solve problems. involves creating algorithms for performing actions on, and with, the data that has been modelled

Question 8

composition

Answer 8

combining procedures into compound procedures

Question 9

problem abstraction / reduction

Answer 9

details are removed until the problem is represented in a way that is possible to solve because the problem reduces to one that has already been solved

Question 10

why use meaningful variable names

Answer 10

easier to follow program process

Question 11

array

Answer 11

finite, ordered set of elements of the same data type

Question 12

what is a structured programming approach

Answer 12

• decomposition of a problem
• makes use of subroutines
• makes use of control structures - sequence / selection / iteration

Question 13

what is a subroutine

Answer 13

named block of code performing a specific task within a program

Question 14

features of a structured program

Answer 14

• selection, iteration, sequence
• modular
• exit gate

Question 15

advantages of modular programming

Answer 15

• easy to understand subroutines as small units of code - easier to understand, debug, maintain
• subroutines can be tested independently, shortening dev time
• modules can be reused in other programs

Question 16

why use exception handling

Answer 16

• avoid errors which will cause the program to crash

Question 17

tasks performed during design soft-dev stage

Answer 17

• data structures specified
• algorithms / ui / screen designs designed
• design appropriate module structure

Question 18

task performed during technical soft-dev stage

Answer 18

• implementation / writing of code

Question 19

task performed during testing soft-dev stage

Answer 19

• system tested for presence of errors, using selected test data covering normal, boundary and erroneous data
• testing for logic errors, syntax errors, runtime errors

Question 20

task performed during evaluation stage

Answer 20

• system evaluated according to given criteria

Question 21

erroneous data

Answer 21

data outside of expected range and/or wrong data type

Question 22

strategies for problem solving

Answer 22

• exhaustive search
• binary search

Question 23

exhaustive search

Answer 23

trying every possible method / searching every possible item

Question 24

linear search

Answer 24

search item compared with each element in list in linear fashion

looks at, on avg, n/2 items

Question 25

binary search

Answer 25

• look at middle item
• if not correct item, if middle item greater than one being sought, discard second half, vice versa
• repeat until item found

if a list of data has 2^n items, it will look at, at max, n items

Question 26

top-down design

Answer 26

decomposition of a task, where problems broken down until simple enough to be written as self-contained modules

Question 27

what does a good algorithm feature

Answer 27

• should allow for invalid inputs
• should execute efficiently, in as few steps as possible
• designed in an easily understandable / modifiable way
• always terminates at some point

Question 28

bubble sort

Answer 28

in an array of n items:
- go through array, comparing each item with item next to it
- if item greater, swap
- last item in the array will be in correct place after first pass
- repeat n - 1 times, reducing by 1 on each pass

Question 29

representational abstraction

Answer 29

representation arrived at by removing unnecessary details

Question 30

abstraction by generalisation or categorisation

Answer 30

grouping by common characteristics to arrive at a hierarchical relationship of the ‘is a kind of’ type

Question 31

information hiding

Answer 31

process of hiding all details of an object that do not contribute to its essential characteristics

Question 32

procedural abstraction

Answer 32

represents a computational method, actual values used in a computer separate from overall design - involves only writing a subroutine and passing abstracted parameters

Question 33

functional abstraction

Answer 33

particular computation method is hidden - think of it like a primary school number box thing, where you put in inputs and you get outputs, and you don’t know what happens inside of the box

Question 34

data abstraction

Answer 34

details of how data are actually represented are hidden - separate the way that a compound data object is used, from the details of how it is constructed

Question 35

what is a finite state machine

Answer 35

abstract model of how a machine reacts to an external event

Question 36

in a finite state machine:

Answer 36

• machine can only be in one state at a time
• transition can occur, where machine changes state in response to an event / condition
• FSM defined by a list of its states and the condition for each transition

Question 37

finite state automaton

Answer 37

FSM with no output

Question 38

FSM symbols and their meanings

Answer 38

• empty circle - state
• circle with arrow pointing to it - start state
• circle with inner circle - accept state

Question 39

use of parameters in context of subroutines

Answer 39

specifies any values that must be passed to a subroutine when it is called