Computational thinking

Question 1

what is computational thinking?

Answer 1

the ability to think logically about a problem and applying techniques for solving it

Question 2

what are the components of computational thinking?

Answer 2

• abstraction
• decomposition
• pattern recognition
• algorithm design

Question 3

what is abstraction?

Answer 3

a way of separating the logical and physical aspects of a problem - you remove excessive details about the problem until you reach a representation of the problem with only key features

Question 4

what is involved in abstraction?

Answer 4

• designing a model that represents reality (simple queue to climate change)
• certain characteristics of objects/systems are removed so that it is reduced to a simple set of characteristics

Question 5

how does modelling and simulations relate to abstraction?

Answer 5

• building models of real world phenomena help solve problems by discarding irrelevant details
• then design algorithms + data structures the implement it in program code and execute it

Question 6

what is representational abstraction?

Answer 6

creating a simpler version of something real by leaving out unnecessary detail and keeping only what is useful - eg. the London Underground Map

Question 7

what is abstraction by generalisation?

Answer 7

grouping things together based on their shared characteristics - important in OOP eg. when you create instances of a class with different details in each

Question 8

what is procedural abstraction?

Answer 8

creating a procedure or subroutine to do a task without having to think about the internal workings every time you use it - focus on functionality rather than logic + easily reusable
eg. find the surface area of an object instead of a specific chopping board

Question 9

what is functional abstraction?

Answer 9

the details of how a computation is carried out is hidden (a black box) - input given, processed, output returned - user only needs to know how to call a function - enhances flexibility of code

Question 10

what is data abstraction?

Answer 10

• technique to separate the way a compound object is used from the details of how it is constructed
• eg. stack - dont worry about how it is implemented so long as it works
• allows creation of abstract data types

Question 11

what is problem reduction?

Answer 11

generalising or reducing a problem to one that has already been solved - break complex problems into smaller manageable problems
solve with standard algorithms or specialised ones

Question 12

what are the 2 main challenges in producing a solution?

Answer 12

• correct algorithm - must work for all possible inputs
• efficient algorithm - must not waste compute power since it often handles lots of data

Question 13

what is thinking ahead?

Answer 13

• take the initial abstract model and add detail to it until it has been transformed into a computer program
• think ahead about components of a program and how they will be handled in the best way possible
• allows developers to consider problems or difficulties that may arise

Question 14

what is an input to a problem?

Answer 14

any data required to solve the problem - inputted by the user

Question 15

what is an output to a problem?

Answer 15

the results passed back once inputs have been processed and the problem has been solved - must be of a suitable data type, structure and method depending on the situation

Question 16

how do designers try to make solutions using inputs and outputs?

Answer 16

• first think about outputs required based on user requirements
• then identify inputs required + processing needed on them to get outputs

Question 17

why is formally documenting inputs and outputs good?

Answer 17

there is no ambiguity in what must be supplied to the subroutine + what must be returned

Question 18

what are preconditions?

Answer 18

requirements defined by the problem that must be met before a program can be executed - prevents execution failure/invalid answers

Question 19

what are the advantages of specifying preconditions in documentation?

Answer 19

• makes program components reusable
• cuts out unnecessary checks - programmers know what checks need to be done
• shorter + less complex program
• saves time on debugging + maintenance

Question 20

what is the purpose of preconditions?

Answer 20

ensure necessary checks are carried out before execution of a subroutine (by user or subroutine) - makes them more reusable

Question 21

what are reusable programming components?

Answer 21

• well defined + documented functions + procedures that can be used in different programs
• can be added to a library + imported wherever needed

Question 22

why are reusable program components useful?

Answer 22

• saves time writing + testing functions that have already been written, debugged and tested (large project)
• following programming standards makes them easier to use for other programmers

Question 23

what are some typical standards for reusable modules?

Answer 23

• inputs, outputs, preconditions documented
• standard convention for variable names
• all variables should be local to the module
• standard format for documentation - what module does, who wrote it + when
• explanations of code where needed
• no module should be greater than 1 page of code

Question 24

what is caching?

Answer 24

temporarily storing instructions/values in cache memory after use in case they are needed again and can be accessed quickly - eg. last few instructions executed, result of earlier computation

Question 25

what is webcaching?

Answer 25

webpages and their contents recently looked at are stored in cache - content can be loaded without delay + text + images dont need to be downloaded multiple times, freeing bandwidth

Question 26

what is prefetching?

Answer 26

algorithms predict which instructions are likely to be fetched soon - loaded + stored in cache before being fetched - less time spent waiting for instructions to be loaded from hard disk to RAM

Question 27

what are the advantages of caching?

Answer 27

- faster access to cached resources - save on costly bandwidth use - reduced load on web services in a client server env

Question 28

what are the disadvantages of caching?

Answer 28

- there is no guarantee the predicted data will be used - valuable space taken up unnecessarily - larger caches take a while to search - cache size limits need to be in place to maintain speed - can get a stale copy of resource if there have been changes made after its loaded into cache - can be difficult to implement

Question 29

what is thinking procedurally?

Answer 29

breaking down a problem into smaller parts which are easier to understand so easier to design

Question 30

what is procedural decomposition?

Answer 30

breaking a large complex problem into a number of subproblems so that each subproblem completes an identifiable easily solvable task.

Question 31

why is procedural decomposition useful?

Answer 31

- makes the problem more feasible to manage - can be divided between a group of people based on each person's skillset

Question 32

what is stepwise refinement?

Answer 32

the process of breaking down a programming problem into a series of steps - used in structured programming

Question 33

what is a hierarchy chart?

Answer 33

- a diagram used to show how a large problem is broken down into smaller subproblems organised levels - higher levels = problem overview - lower levels = detailed components of the problem

Question 34

why are hierarchy charts useful?

Answer 34

- problems are fully decomposed - simpler design, programming + testing - well-documented subroutines with preconditions can be easily tested + updated - shows how subroutines are related

Question 35

what are the main techniques used in structured programming?

Answer 35

- modularisation - program structure + organisation (eg. break down into subroutines) - structured code - for individual modules use sequence, selection, iteration - recursion - procedure/rule is repeated

Question 36

is the order of steps in a solution important?

Answer 36

YES! The order which subroutines are executed and how they interact with each other matters eg. in a game the user shouldnt be able to play a level they havent unlocked yet

Question 37

what are some benefits of modularisation?

Answer 37

- easier/quicker to write, test + debug programs - each subroutine can be individually tested - modules can be reused within the program - save frequently used modules in a library - several programmers can work simultaneously on different modules -> less development time - new features can be added by adding new modules - easier to maintain programs

Question 38

what are the features of a good algorithm?

Answer 38

- has clear + precisely stated steps that produce correct output for all valid inputs - should allow for invalid inputs - must always terminate at some point - should have as few steps as possible - efficient - should be designed so that other people can understand it + modify if necessary

Question 39

what are some common tools used to design algorithms?

Answer 39

- hierarchy charts - identify major tasks + breaking down into subtasks - flowcharts - get down initial ideas for individual subroutines - pseudocode - easily translates into program code

Question 40

what sorts of decisions need to be made when building a program?

Answer 40

- which programming paradigm? - which programming language? - what input devices? - what output devices? - how will i interact with these devices?

Question 41

what is a decision?

Answer 41

a result reached after some consideration

Question 42

how are decisions represented in a flowchart?

Answer 42

diamond shaped icon - with an arrow for yes and an arrow for no

Question 43

what factors affect your decision making process?

Answer 43

- what is most effective? - what is most convenient? - is this option reasonable/feasible?

Question 44

what is a decision point?

Answer 44

the specific points where a program must make a choice or decision regarding the flow of execution - normally an if statement, for loop, while loop

Question 45

what is a validation routine?

Answer 45

a routine that checks whether a user has entered a value fit for processing - can involve tricky boolean conditions

Question 46

what validation routine questions are used to check whether a password is correct?

Answer 46

- what happens if the user enters an incorrect password? - how many tries are allowed? - will there be a way of giving them a hint? - will there be a forgot password option to receive a new password by email?

Question 47

what is concurrent processing?

Answer 47

where each task is given a slice of processor time to make it look like tasks are being completed simultaneously when in reality they are executed sequentially

Question 48

what is parallel processing?

Answer 48

when multiple processors are used to complete more than one task simultaneously

Question 49

what are the benfits of concurrent processing?

Answer 49

- number of tasks completed in a given time increases - less time wasted waiting for an input/user interaction - other tasks can be completed

Question 50

what are the drawbacks of concurrent processing?

Answer 50

- can take longer to complete when lots of users or tasks are involved - processes cant be done at once - overhead in coordinating and switching between processes - reduces program throughput - not all tasks are suited to being broken up and performed concurrently

Question 51

give some examples of real world examples of concurrent processing?

Answer 51

- numerical weather predictions - requires around a quadrillion calculations to be done within 3-24hrs - done by special processors that can do calculations concurrently - Dual/quad core processors - most phones/PCs have 2-4+ cores - operating system assigns different tasks to each - search engine - when multiple tabs are open all cores can be used at full capacity - phones - video editing, image processing, facial recognition, 3D games + applications, virus scans, etc.