OCR A Level Computer Science Paper 2 Practice Questions and Answers

Abstraction a way of separating logical and physical parts of a problem e.g. the london underground map. You get rid of unnecessary details Problem abstraction where you keep removing details until the problem reduces to one that has already been solved Modelling and Simulation Building a model of a real world object can be used to solve a particular problem such as Aircraft simulation, Climate change models Precondition is the logic part of a statement statement that has to be true for the processing part of the algorithm before it can function Specifiying a precondition before creating an algorithm ensures The data is ok to process e.g. if it was empty it could cause the program to crash. The function is reusable It reduces unnecessary checks It makes programs easier to debug and maintain It makes programs clearer and shorter Progamming standards that make programs easy to resuse include Documenting inputs, outputs and preconditions Variables should use camelCase or PascalCase All variables should be local to that module The documentation should contain information such as who made it, what it does and when it was written. The code should be annotated where necessary The module should not be greater than one page of code Caching the temporary storage of data instructions so that the information can be achieved quicker than performing a calculation e.g. frequently accessed web pages can be stored locally The advantages pf caching It's faster to access information that is cached This saves the cost of bandwidth It also reduces the load on web services in a client-server environment Disadvantages of caching There is slower performance if the result is not found in the cache