A-level Computing/CIE/Fundamental Problem-solving and Programming skills/Algorithm design and problem-solving

Specification link

Algorithms

show understanding that an algorithm is a solution to a problem expressed as a sequence of defined steps
use suitable identifier names for the representation of data used by a problem
- summarise identifier names using an identifier table
show understanding that many algorithms are expressed using the four basic constructs of assignment, sequence, selection and repetition
show understanding that simple algorithms consist of input, process, output at various stages
document a simple algorithm using:
- structured English
- pseudocode (on the examination paper, any given pseudocode will be presented using the Courier New font)
- program flowchart
use the process of stepwise refinement to express an algorithm to a level of detail from which the task may be programmed
decompose a problem into sub-tasks leading to the concept of a program module (procedure/function)
show an appreciation of why logic statements are used to define parts of an algorithm solution
use logic statements to define parts of an algorithm solution

Structure chart

use a structure chart to express the inputs into and output from the various modules/procedures/functions which are part of the algorithm design
describe the purpose of a structure chart
construct a structure chart for a given problem
derive equivalent pseudocode from a structure chart

Corrective maintenance

perform white-box testing by:
- selecting suitable data
- using a trace table
identify any error(s) in the algorithm by using the completed trace table
amend the algorithm if required

Adaptive maintenance

make amendments to an algorithm and data structure in response to specification changes
analyse an existing program and make amendments to enhance functionality

Structure Charts

A Structure Chart in software engineering is a chart which shows the breakdown of a system to its lowest manageable parts. They are used in structured programming to arrange program modules into a tree. Each module is represented by a box, which contains the module's name. The tree structure visualizes the relationships between modules, showing data transfer between modules using arrows. Structured Charts are an example of a top-down design where a problem (the program) is broken into its components. The tree shows the relationship between modules, showing data transfer between the models.

Symbol

Name

Meaning

Module Name

Process

Each Box represents a programming module, this might be something that calculates the average of some figures, or prints out some pay slips

Data Couple

Data being passed from module to module that needs to be processed.

Flag

[Extension - you don't need to know this for the exam] Check data sent to process to stop or start processes. For example when the End of a File that is being read is reached, or a flag to say whether data sent was in the correct format

Selection

A selection in a Structure Chart is determined by the diamond symbol. This means a condition will be checked and depending on the result, different modules will be executed.

Iteration

Using the semi circular arrow we can represent iteration in Structure Charts.