1.
Revision
Michael Heron

2.
Introduction
• In today’s lecture we are going to round off our discussion of
programming with a revision of topics.
• The theoretical side of these at least.
• This relates to the examination portion of the module.
• Important to understand the concepts for this.
• Code of secondary importance.

3.
What Is A Program?
• A program is a series of statements to the computer.
• Computers are stupid
• Humans are clever
• Need to ‘talk down’ to the computer
• Process of arriving at a working program very complicated.
• Involves the interaction of many skills.

4.
Representing Information
• Information in a computer program is represented by
variables.
• These are stored in the computer’s memory.
• Variables stand in place of literal values.
• We don’t know what they will be when we run the program.
• Used to deal with ambiguity.
• Can be many different types.

5.
Flow of Execution
• All programs have a flow of execution.
• This determines in what order the code statements are executed.
• By default, flow of execution is sequential.
• Statements are executed one after the other.
• We have access to many flow control operations to change
that.
• These permit us to change the order in which code is executed.

6.
Flow of Execution
• Repetition structures are used to repeat sections of code.
• They fall into two categories.
• Unbounded loops, when we don’t know how many times to
iterate.
• Bounded loops, when we do.
• For loops are bounded loops.
• While loops are unbounded loops.
• Also exist a do-while loop, with more situational use.

7.
Flow of Execution
• Selection structures allow us to choose between different
paths of execution.
• If lets us provide code that might be executed if conditions are
met.
• If-else lets us provide between two mutually exclusive course of
action.
• If-Else if allows for more fine-grained control.
• Switch statement exists as a syntactic nicety.
• It makes code more readable.

8.
Arrays
• Representing data as single variables very limited.
• Many real world situations require something more
comprehensive.
• Arrays exist as a collection of related data.
• A list of names, a list of ages, etc
• Arrays are syntatically amenable to manipulation with other
structures.
• For loops in particular.

9.
Arrays
• Arrays serve as the basis for more complicated data
structures.
• They can be 1D, 2D, or as many dimensions as we like.
• Arrays are made up of elements which are identified by
indices.
• The number of indices is dependant on how many dimensions
the array has.
• It’s like a variable with many different compartments.

10.
Functions
• Incorporating all program code into a single main function is
very limited.
• Hard to write
• Hard to read
• Hard to maintain
• Functions allow us to split up the functionality between
smaller units.
• Functions, or methods
• Same thing with different names.

11.
Functions
• Functions are uniquely identified by their signatures.
• Their name, and the order and type of their parameters.
• Parameters get sent into functions as a way of providing
information.
• Functions can return a value to their calling function.
• To give information back.

12.
Functions and Variables
• Functions introduce a new issue with regards to variables.
• That of Scope
• In a program, variables have one of three kinds of scope.
• Local
• Global
• Class-wide

13.
Pointers
• Variables represent an abstraction.
• They are not the memory addresses, but the contents of the
memory addresses.
• Pointers allow us to access memory locations directly.
• Useful for several reasons.
• Works through the use of two operators
• *, which is the dereference operator
• &, which is the reference operator.

14.
Program Correctness
• Most programs are not very correct.
• They crash, or misbehave.
• It’s very hard to create correct computer programs.
• Beyond the ability of Mortal Ken
• This a direct result of the way digital data is represented.
• We can take a structured, systematic approach to this.
• By creating and following a testing strategy

15.
Testing
• Testing breaks down into two key families.
• Black box testing, which tests only inputs and outputs.
• White box testing, which tests only the flow of execution through
the program.
• Testing based on the creation of test cases.
• These stress ‘high risk’ parts of the system.
• A good testing strategy is one designed to uncover flaws.

16.
Debugging
• Getting a program running is the easy thing.
• Getting it working is more difficult.
• Debugging is a complex task requiring patience and a
particular mindset.
• It involves tracking down often complex misbehavior.
• It is a process intricately linked to programming.
• But a separate and distinct step.

17.
Objects
• C++ is an object oriented language.
• This introduces new difficulties in development.
• Object oriented programming is built on two main structures.
• The class, which is a blueprint
• The object, which is a specific instance of a class.
• Classes define our structural side of the program.
• Objects define our dynamic side.

18.
Objects and Classes
• Classes sit idle until we create objects from them.
• This process is called instantiation.
• The class defines the structure.
• The attributes
• The methods
• The object defines the state.
• The value each of the attributes has.

19.
Encapsulation
• Good object design is very difficult.
• It takes years and years of practise and making mistakes.
• Some principles exist to aid in design.
• Encapsulation is the principle of tying data and the methods that act
on that data together.
• We can protect the delicate innards of an object using visibility
modifiers on the data.
• Private, Public, Protected
• The set of public methods exposed defines the object’s interface.

20.
Inheritance
• Inheritance is the technique of allowing one class to
incorporate methods and attributes defined in another.
• The child class inherits the methods and attributes of the parent.
• Useful for many reasons.
• Maintenance
• Reusability
• Cohesion of interface

21.
Object Design
• Hard to assess a particular object hierarchy.
• Some metrics exist
• Cohesion
• Coupling
• Impact of Change
• Important to create objects in the right way.
• Black box design
• Incorporate placeholders
• Compile early and often

22.
File Handling
• Input and Output in C++ is handled via streams for the most
part.
• cout and cin are examples of streams.
• File I/O in C++ is handled as an extension of this idea.
• Create an appropriate object
• Manipulate it using << and >>
• Close it when you’re done

23.
Stream I/O
• Streams in C++ are very versatile.
• They can be manipulated using stream manipulators.
• Techniques are shared between keyboard / monitor I/O and
file I/O
• What works for one will work for the other.
• This is powered by inheritance.
• They all inherit from the same basic structure.

24.
Parsing
• Most of the data you pull into a system will not be in a format
suitable for processing.
• Necessary to parse data into a suitable format.
• Various parsing routines exist.
• Tokenization
• Object representation
• Data conversion
• Usually necessary to ‘roll your own’
• Data representation is too important to leave to ‘off the shelf’
solutions.

25.
Summary
• Summarising a summary of the module is a crazy thing to do
• So instead I will put some jokes.
• Two fish are in a tank. One turns to the other and says ‘Do you
know how to drive this thing?’
• The other says ‘My word! A talking fish!’
• Have you heard about the new pirate movie? It’s rated
AaaaAaaaaAaarrrrRrr!