CIE Computer Science (I)GCSE - Topic 7

What are the four stages in the program development life cycle?

analysis, design, coding and testing

What happens in analysis?

abstraction, decomposition of the problem, identification of the problem and requirements

What happens in design?

decomposition, structure diagrams, flowcharts, pseudocode

What happens in coding?

writing program code and iterative testing

What happens in testing?

testing program code with the use of test data

What is a computer system made up of?

sub-systems, which are made up of further sub-systems

How are problems solved using a computer system?

By decomposing the problem into its component parts

What are the 4 component parts of any computer system?

inputs, processes, outputs and storage

What are inputs?

the data used by the system that needs to be entered while the system is active

What are processes?

the tasks that need to be performed using the input data and any other previously stored data

What are outputs?

information that needs to be displayed or printed for the users of the system

What is storage?

data that needs to be stored in files on an appropriate medium for use in the future

What is totalling?

keeping a total that values are added to

What is counting?

keeping a count of the number of times an action is performed

What is finding the maximum, minimum and average values?

finding the smallest and largest values in a list, as well as calculating the average (mean) of all the values in a list

What is linear search?

a search which inspects each item in a list in turn to see if the item matches the value searched for

What is bubble sort?

Each item is compared with the adjacent item and swapped if necessary

Why are validation checks needed on input data?

so that computer systems only accept data inputs that are reasonable and accurate

What are the 6 types of validation checks?

range, length, type, presence, format and check digits

What are range checks?

checks that the value of a number is between an upper value and a lower value

What are length checks?

it checks that either:

- the data contains an exact number of characters

- the data entered is a reasonably number of characters

What are type checks?

it checks that the data entered is of a given data type

What are presence checks?

checks to ensure that some data has been entered and the value has not been left blank

What are format checks?

checks that the characters entered conform to a pre-defined pattern

What are check digits?

the final digit included in a code, calculated from all the other digits in the code to identify incorrect digits, order changes, omitted or extra digits, and phonetic errors like 13 instead of 30

why are verification checks needed to be made on input data?

to check that data has been accurately copied from one source to another

what are double entry checks?

- when data is entered twice, sometime by different operators, so that the computer system can compare both entries

- if the entries are not the same, then an error message requesting for the data to be entered again is made

what are screen/visual checks?

a manual check completed by the user who is entering the data, where the user is asked to confirm the data displayed on screen is correct before continuing

what is normal test data?

Data which should be accepted by a program without causing errors

what is abnormal test data?

Data that should be rejected by the program.

what is extreme test data?

The largest and smallest acceptable values, e.g. 0 and 100 for a mark

what is boundary test data?

The largest/smallest acceptable values AND the corresponding smallest/largest rejected values, e.g. 0,-1 and 100,101 for a test score

what are terminator flowchart symbols?

- used at the beginning/end of a flowchart

- shown by a rounded rectangle

what are process flowchart symbols?

- used to show actions, e.g. values assigned to variables

- shown by a rectangle

what are input/output flowchart symbols?

- used to show the input of data and the output of information

- shown by a parallelogram

what are decision flowchart symbols?

- used to decide which action is to be taken next, always resulting in two outputs

- can be used for selection and repetition/iteration

- shown by a diamond

how do you assign a value to a variable in pseudocode?

by using an arrow

what are the two types of conditional statement?

- IF...THEN...ELSE...ENDIF

- CASE OF...OTHERWISE...ENDCASE

how does IF...THEN...ELSE...ENDIF work?

- it is a condition that can be true or false, e.g.

IF Age < 18

THEN

OUTPUT "Child"

ELSE

OUTPUT "Adult"

ENDIF

how does CASE OF...OTHERWISE...ENDCASE work?

- when there is a choice between several values, e.g.

CASE OF Grade

"A" : OUTPUT "Excellent"

"B" : OUTPUT "Good"

"C" : OUTPUT "Average"

OTHERWISE OUTPUT "Improvement is needed"

ENDCASE

what is the pseudocode operator for greater than?

>

what is the pseudocode operator for less than?

<

what is the pseudocode operator for equal?

=

what is the pseudocode operator for greater than or equal?

>=

what is the pseudocode operator for less than or equal?

<=

what is the pseudocode operator for not equal?

<>

what is the pseudocode operator for both?

AND

what is the pseudocode operator for either?

OR

what is the pseudocode operator for not?

NOT