SLR18, SLR19, SLR20, SLR21

Abstraction

Process of separating ideas from reality. hiding unnecessary details and showing details important in context

The need for abstraction in programs

• ↓ processing requirements

• ↓ memory requirements

• ↓ complexity

• Simplify programming

• Without it its difficult & confusing to display certain features

Need for thinking ahead

• Maximise code efficiency

• Minimise errors

Preconditions

Conditions that already exist and could affect how you devise solution to problem

Benefits of reusable code

• Reduce dev time & cost

• Save system resources

• Reduce redundant code

Advantages of using software libraries

• Routine already compiled - tested & error free

• Save work for programmer

• May be used multiple times

• Allow use other programmers expertise

• May require fewer devs

External reuse

Selling component to 3rd party

Top-down modular design using structure diagrams

• Can break down problem into top-down modular design using stepwise refinement

• Using top-down design, task is split into smaller sub-tasks

• End up with sub-task that performs single function/task

• Lowest level sub-task assigned to individual programmers/small teams

Benefits of subprograms

• Written once, called multiple times

• Can reuse in other programs

• Can be tested and modified individually

• Breaks program into sections

• Reduces repeating/redundant code

Caching

Instructions/data retrieved from secondary storage & placed into main memory, remaining there in case they are needed

Caching benefits

• Used by web pages to reduce number or requests from client to web server and visa versa

• Overall caching increases speed and efficiency

Caching drawbacks

• Difficult to implement due to nature of predictive logic

• Wrong data often fetched

• Maintaining correct sequence of instructions & data items in these circumstances can be problematic