Unit 4

Question 1

Identify inputs and outputs required in a solution

Answer 1

Cycle: Input; Processing; Output; Feedback

Question 2

Sequential

Answer 2

Following in logical orders/sequences

Question 3

Preconditions

Answer 3

Constrains the state of a system before the next sector of code starts

Question 4

Post conditions

Answer 4

Conditions after code has been executed

Question 5

What to do if there’s an exception?

Answer 5

Inform developer; then crash

Question 6

What to do if there’s an error?

Answer 6

Inform user; but keep running

Question 7

Concurrent

Answer 7

When two or more processes are using the same resources at the same time

Question 8

Describe how concurrent processing can be used to solve a problem

Answer 8

Increases: Computation speed; Complexity of programming language and hardware. Reduces: Complexity of array operations within loops; matrix multiplication/ sorting/ merging files. I(CS; CPL; H) R(CAOL; MM; S; MF)

Question 9

How do you evaluate the decision to use concurrent processing in solving a problem?

Answer 9

Saved or wasted time? Saved or spent money? Physically possible? Consequence of not doing it?

Question 10

Advantages of concurrency

Answer 10

Time Cost

Question 11

Disadvantages of concurrency

Answer 11

May get in each others way Harder to supervise

Question 12

Abstraction

Answer 12

Removing characteristics from something in order to reduce it to a set of essential characteristics. It’s a technique for managing complexity.

Question 13

Why is abstraction required?

Answer 13

Reduces complexity; enables concentration on essential; ignores distracting details and essential to problem solving.

Question 14

How to distinguish between real and abstract?

Answer 14

DETAILS

Question 15

IB assumptions about collections are

Answer 15

Unordered lists Unknown length

Question 16

Operations (5 PseudoCode operations)

Answer 16

.addItem() .resetNext() .hasNext() .getNext() .isEmpty()

Question 17

.addItem()

Answer 17

Adds an item to the collection

Question 18

.resetNext()

Answer 18

Starts at the beginning of the collection

Question 19

.hasNext()

Answer 19

To see if it has another item

Question 20

.getNext()

Answer 20

retrieves next data point from collection

Question 21

.isEmpty()

Answer 21

Checks whether its empty

Question 22

Most efficient search algorithm?

Answer 22

Binary; Olog(N) notation; only works on sorted lists

Question 23

Sequential search

Answer 23

Slower; O(N) notation

Question 24

Bubble sort

Answer 24

Quits early if no swaps occur; but LOTS of swaps happen. O(N^2)

Question 25

When bubble sorting on a list

Answer 25

Compares and swaps every two numbers

Question 26

Selection sort

Answer 26

No quit early; always N passes. O(N^2)

Question 27

Flow chart shapes (bubble; parallelogram; rectangle and diamond)

Answer 27

Bubble: Terminator Parallelogram: Input/ Output Rectangle: Process Diamond: Decision

Question 28

What effects run time?

Answer 28

Hardware Abstract data types Compiler Efficiency Programmers skills Complexity Size of input (H; ADT; CE; PS; C; IS)

Question 29

Worse case scenario

Answer 29

Max run time Number of times the principal activity of the algorithm is performed

Question 30

Best case scenario

Answer 30

Specific instances of input size N

Question 31

Average case scenario

Answer 31

Most useful General case

Question 32

Fundamental operations of a computer

Answer 32

Add; Compare; Retrieve; Store.

Question 33

Complex operation example

Answer 33

Finding the biggest number in an array

Question 34

Low level language

Answer 34

Closer to binary; Machine code or Assembly

Question 35

High level language

Answer 35

Java; C++; HTML

Question 36

Natural language

Answer 36

Varying vocab Ambiguous Grammar & Syntax inconsistent

Question 37

Computer language

Answer 37

Fixed vocab Unambiguous meaning Grammar & Syntax consistent

Question 38

Why grammar and syntax is important

Answer 38

Easy to learn and use Less compilation and logical errors

Question 39

Need for High Level languages

Answer 39

Similar to human language Needs for computer systems have expanded Time constraints - too long to write machine code (HL; NCS; T)

Question 40

Need for Low Level languages

Answer 40

Close to binary code that's used to process instructions

Question 41

Compiler

Answer 41

Translates from a high level language to a low level (in batches)

Question 42

Interpreter

Answer 42

High level to intermediate; then executed by CPU

Question 43

Why you need compliers and interpreters?

Answer 43

High level to low level langauge Translated into machine code for CPU to execute

Question 44

Why do you need BOTH?

Answer 44

Interpreter is faster and warns about syntax errors; easier when debugging Compiler needed when there's a need to produce executable version of program

Question 45

Assembler

Answer 45

Assembly to machine code (mnemonics -> binary)

Question 46

Variables

Answer 46

Storage locations; naming memory locations with a name and data type that can't be changed.

Question 47

Constant

Answer 47

Identifier with associated value that doesn't change.

Question 48

Operator

Answer 48

Set of characters that represents an action (CRA)

Question 49

Object

Answer 49

Instance of a class

Question 50

Advantages of modular design

Answer 50

Code *reusability*; Eases program *organization* and makes future *maintenance* easier (CR; EPO; ME)

Question 51

Need for sub programmes

Answer 51

Breaks down tasks into more manageable sections Distributes development Code Reusability Program readability (BM; DD; CR; PR)

Question 52

Bubble sort algorithm

Answer 52

int temp; loop i from 0 to array.length-1 loop j from 0 to array.length-1 if array[i] > array[i+1] then temp = array[i] array[i] = array[i+1] array[i+1] = temp end if end loop end loop

Question 53

Selection sort algorithm

Answer 53

int temp; loop i from 0 to array.length-1 loop j from i+1 to array.length if array[i] > array[j] then temp = array[i] array[i] = array[j] array[j] = temp end if end loop end loop

Question 54

Sequential search algorithm

Answer 54

loop for i from 0 to array.length if searchkey == array[i] then ouput searchkey; 'has been found!'break; end loop

Question 55

Finding the minimum and maximum in an array

Answer 55

int min = array[0] int max = array[0] loop i from 0 to array.length if min > array[i] then min = array[i] end if else if max < array[i] then max = array[i] end else if end loop output 'min ='; min; 'max ='; max

Question 56

Binary Search Algorithm

Answer 56

input key low = 0 high = array.length-1 found = -1 loop i while found == -1 && low <= high mid = (low + high) div 2 if array[mid] == key then found = mid else if key < array[mid] then high = mid - 1 else low = mid + 1 end if end while if found >= 0 then output key; ' was found!'else output key; ' was not found!'end if

Question 57

Hours given minutes

Answer 57

Div 60

Question 58

Minutes remaining

Answer 58

Mod 60 (This was a past paper question!)