2.2 Problem solving and programming Flashcards
What are the three types of programming constructs?
sequence
branching
iteration
Explain what we mean by sequence as a programming construct
when code is executed line-by-line, from top to bottom
Explain what we mean by branching as a programming construct
when a particular block of code is met if a specific condition is met
examples are if and else statements
Explain what we mean by iteration as a programming construct
blocks of code which loop
can be either:
count controlled- blocks of code looping over a certain number of times
condition controlled- blocks of code looping until a specific condition is met
examples are DO, WHILE, FOR loops
Explain recursion
When a subroutine calls upon itself during its execution
-continues until a stopping condition is met
What are some advantages to using recursion? (2)
-code can be represented in fewer number of lines
-easier to express some functions recursively e.g. factorial
What are some disadvantages to using recursion (2)
-risk of stack overflow if memory runs out
-difficult to trace
What is a scope and how is this related to variables?
-variables can be defined with a global or local scope
-a scope is the section of code where the variable can be accessed
Explain what local variables are and their characteristics
variables which can only be accessed within the subroutine where they were defined
Explain what global variables are and their characteristics
variables which can be accessed through the whole program
What are some +/- of using local variables? (3, 1)
+won’t affect other sections of code
+deleted once subroutine ends so doesn’t take up lots of memory
+multiple local variables with same names but in different subroutines can exist
-need to keep declaring in different sections of code if needed there
What are some +/- of using global variables? (1, 3)
+useful for values that need to be used by multiple parts of the program
-if changed, it will affect other areas of code where it has been called upon
-can unintentionally edit it
-not deleted until program terminates so requires more memory
What is modular programming?
a technique used to split large/complex programs into smaller, self-contained modules
Why is modular programming useful? (3)
-easier to divide tasks between a team and manage projects
-simplifies the process of testing and maintenance (each component can be tested individually
-improves reusability of components
Explain a top down design/modules
-technique to modularise programs
-problem is broken down into subproblems until each is is represented into individual, self-contained modules which perform a specific task
-modules form blocks of code called subroutines
Explain functions
-blocks of code which perform a specific task
-functions return a value
-can pass parameters by value or by reference
Explain procedures
-blocks of code which perform a specific tasks
-procedures output values
-can pass parameters by value or by reference
What do we mean by passing a value by reference?
-address of parameter is given to the subroutine
-value of parameter will be updated at the given address
-changes the original data stored
What do we mean by passing a value by value?
-a copy of the value is passed to the subroutine and discarded at the end
-the original value stored is unaffected
What is an IDE?
integrated development environment
-provides a set of tools to make it easier for programmers to write, develop and bug code
What are some features of IDEs? (7)
-stepping (executes line by line to see how each line effects program)
-variable watch (observes the contents of variable and how they change in real time through execution)
-debugging tools (provides errors in lines during run-time)
-autocompletion
-syntax highlighting
-breakpoints
What is a class?
a template for an object
-defines state and behaviour for an object
How can we define the state and behaviour of an object?
state- using attributes
behaviour- methods
What is an object?
a particular instance of a class
What is encapsulation?
when attributes cannot be directly edited (declared as private)
-can only be altered by public methods
-makes the program less complex by protected data from being edited
How do top down designs use encapsulation?
each module is designed to be self-contained
What do we mean by divide and conquer? Where could this be used?
problem solving technique
simplifies complex problems quickly
three parts:
-divide (problem in 1/2 with every iteration)
-conquer (each subproblem is solved, often recursively)
-merge (solutions to subproblems are recombined)
examples: quick sort, merge sort, binary search
What are the various problem solving strategies? (7)
-backtracking
-visualisation
-data mining
-heuristics
-performance modelling
-pipelining
-divide and conquer
Explain backtracking
-problem solving technique implemented using algorithms, often recursively
-methodically builds a solution based on visited pathways found to be correct
-if a pathway is found to be invalid, algorithm backtracks to previous stage
Explain data mining
-technique used to identify patterns or outliers in large data sets collected from a variety of sources (also known as big data)
-trends spotted can aids predictions about the future
Explain heuristics and give an example of where this may be used
-non-optimal, ‘rule-of-thumb’ approach to problem solving
-used to find an approximate solution when the standard solution takes too long to find
-isn’t perfectly accurate/complete
example: A* pathfinding algorithm
Explain performance modelling
-mathematical methods used to test various loads on different OS
-provides cheaper, less time-consuming or safer method of testing applications
Explain visualisation
-data can be presented in a way that is easier for us to understand using graphs, trees, charts etc.
-makes it possible to identify trends that were not otherwise obvious
