01 Problem Solving and Algorithms

GCSE Computer Science 1CP2

Abstraction

the process of removing or hiding unnecessary details so that only the most important points remain.

Algorithm

a precise method for solving a problem. It consists of a sequence of step-by-step instructions that solve a specific problem.

Algorithmic bias

behaviours in computer programs that create unfair outcomes.

Artificial intelligence (AI)

the ability of a digital computer or computer-controlled robot to perform tasks commonly associated with intelligent beings. Intelligent beings are those that can adapt to changing circumstances.

Ascending order

arranging items from smallest to largest (e.g. 1, 2, 3, 4, 5,60ra, b,c, d,e, f).

Assignment

the act of storing a value in a variable. Uses the ‘=’ symbol. The value on the right is stored in the variable on the left.

Boundary data

data that sits on the edge of any test conditions, either above or below.

Bug

an error in program code.

Code review

code is examined to identify poor programming practices, find potential vulnerabilities and check its efficiency.

Comments

a way for programmers to annotate code so that their logic is clear to the reader. Comments are not executed.

Computational thinking

the thought processes involved in formulating problems and their solutions so that the solutions are represented in a form that can be effectively carried out by a computer or human.

Decomposition

breaking down into smaller parts. Both problems and solutions can be decomposed into small parts.

Descending order

arranging items from largest to smallest (e.g. 6, 5, 4, 3, 2, lorf,e,d,c,b,a).

Divide and conquer

an algorithm design that works by dividing a problem into smaller and smaller sub-problems, until they are easy to solve. The solutions to these are then combined to give a solution to the complete problem.

Domain Name System (DNS)

a directory of domain names and equivalent IP addresses.

Efficiency

measured by number of compares, number of passes through a loop, or use of memory.

Evaluation

making judgements against requirements, about efficiency, and whether there are other solutions.

Flowchart

a graphical representation of an algorithm. Each step in the algorithm is represented by a symbol. Symbols are linked together with arrows showing the order in which steps are executed.

Generalisation

taking an algorithm that solves one specific problem and adapting it so that it solves similar or new problems.

Heuristics

a type of algorithm capable of finding a solution to a problem quickly and easily, by using a combination of trial and error and educated guesswork to cut corners and eliminate less likely alternatives. Heuristic algorithms don’t always find the best solution, but they will usually find one that works. Some anti-malware software uses heuristics to detect malware by its behaviour and characteristics.

In-place sort

a sort that does not need to make a copy of the data.

Logic error

an error in an algorithm that results in incorrect, unwanted or unexpected behaviour.

Machine learning

the ability of machines to learn on their own without being programmed. For example, pictures of dogs labelled ‘dog’ will help the algorithm identify the rules to classify pictures of dogs.

Median

the middle item when the items are put in ascending or descending order, e.g. if there are 13 items, then the 7th item is the median.

Optimisation

improvements made to an algorithm or process to increase its efficiency.

Pattern recognition

finding common characteristics of small problems that will allow us to develop solutions to other, perhaps complex, problems.

Recursion

involves a subprogram calling itself, with modified input arguments on each call. Each call reduces the complexity of the problem. After a finite number of calls, an endpoint is reached, then each subprogram completes (unwinds) in reverse order.

Robust software

code that can handle unexpected actions without crashing or producing incorrect output.

Selection

a construct that allows a choice to be made between different alternatives. The selection construct is used to create a branch in a program. The computer selects which branch to follow based on the outcome of a test condition.

Sequence

an ordered set of instructions.

Validation

to check that the data entering a program, by any means, is fit for processing. It must meet specific requirements if it is to be allowed into the program. Validation can’t guarantee that data is correct, only that it meets the criteria for processing.

WHILE construct

allows a group of instructions to be repeated over and over, as long as a test condition is true.

WHILE statement

the Python keyword while allows a group of instructions to be repeated over and over, as long as a test condition is true.