C++ Tutorial

C++ Tutorial
Online Programming Tutorials and Learning
Toolkits Web Site
Front-end Development

By Craig Freeman

Introduction


Welcome to a tutorial on programming in
C++. In this tutorial you will be learning
the basics of coding in this language
including; The #include directive, Inputs,
Outputs, Functions, Variables
declaration, Assignment and Data
Types.

Introduction Continued


This tutorial will also focus on key
concepts such as:

Selection
 Iteration
 Data structure
 Functions, parameters and return values


Preparation


Before beginning these tutorials please
ensure that you have CodeBlocks
installed on your PC. If you do not then
please use the link bellow to download
and install CodeBlocks. If you
experience any issues please use the
helpful information found on the site.



http://www.codeblocks.org/downloads/2
6

The #include directive


The include directive is a method of
calling libraries. These libraries are
found in the pre-processor directive and
added before compiling the program.
These libraries tell the compiler how to
make sense of the program you have
written so that it can be successfully run.

continued


The library added using #include
<iostream> tells the compiler to include the
iostream standard file which tells it how to
handle inputs and outputs.



Another example of a library which can be
added is #include <cstdlib> which among
other things allows the use of a
system(“pause”) which is a command to
pause a running program until a user input
is made.

continued


To test this for yourself please download
the programOne folder below and run
the project file in CodeBlocks



https://drive.google.com/folderview?id=0
B7EEqo1krfWPLWJUZXc5RC1tdUU&us
p=sharing

Using namespace std


Using namespace std is a using directive which tells
the compiler how to logically group code. This means
that all namespace std entities become global
namespace and this means you won't have to use
the std:: for them. In other words this code makes it
so std:: does not have to be used constantly.



An example of this in use can be seen in
programTwo using the link below.



https://drive.google.com/folderview?id=0B7EEqo1krf
WPLWJUZXc5RC1tdUU&usp=sharing

The main() function


A function is a section of code which is run. In
essence it is the holder of the main part of the
code which you want to create.



You can have multiple functions in one file
however the default function which is run first
is always main(). An example of this in use can
be seen in programThree of the link below.



https://drive.google.com/folderview?id=0B7EE
qo1krfWPLWJUZXc5RC1tdUU&usp=sharing

The main() function continued


In programThree it can be seen that
within the main function a second
function is being called. This second
function prints hello world. In this way
the main function is accessed first but
still produces the hello world line.

Inputs and 0utputs


Inputs and outputs require std:: at the
front of each command, however using
namespace std this is not necessary.



An output is made using cout code
which is written as: cout << “what you
want to output” << endl;

Inputs and 0utputs
continued


An input is performed very similarly. The
command starts with cin instead and uses >>
instead of << because instead of sending
something out it is taking something in. An
example of this could be cin >> input;



It is very simple to use and examples of both
can be seen in programFour of the following
link:

Variable Declaration and
Assignment


Looking at programFour again the code
– „string input;‟ can be found on line 9.
This is an example of variable
declaration. Variable declaration is the
method of declaring new variables for
use in a program. For example a
variable named Number could be
declared and used later to perform a
calculation.

Variable Declaration and
Assignment continued


Declaring a variable does not assign a value to it and
most often when performing calculations or functions
a variable with a value is necessary. For instance a
calculator needs input from a user and this input is
sent to variables.



Values can be assigned to variables in two ways.
The first involves assigning a value at the same time
as declaring the variable, and the second is inputting
a value within a function. This can be seen on the
following link within programFive.



https://drive.google.com/folderview?id=0B7EEqo1krf
WPLWJUZXc5RC1tdUU&usp=sharing

logical/arithmetic operators


Operators represent specific actions and
are very useful in programming. A logical
operator is used to logically combine
and compare Boolean conditions or
expressions. A few examples of logical
operators can be seen below.
Operator

Meaning

&&

AND

!

NOT

||

OR

continued


The AND logical operator can be used when making a selection
by telling the statement that it must be both statements.



The OR operator can be used in the same way except that it
can be either statements



And the NOT operator would mean that the next step of the
program should only be done if the result being measured is not
the same as the argument in the condition.



Some of these can be seen in action within programSix found
within the below folder.



https://drive.google.com/folderview?id=0B7EEqo1krfWPLWJUZ
Xc5RC1tdUU&usp=sharing

continued
programSix was built to prove the following
statement:
 “The maximum value for a unsigned int is
greater than the maximum value for a
signed int and the minimum value for a int
is less than the minimum value for an short
int or an unsigned int.”
 It does this by declaring all of the relevant
values and then using an if statement to
find out if this is true or false using logical
operators.


continued


Arithmetical operators are much like
logical operators but use mathematical
methods. Examples of arithmetic
operators can be seen below.
Operator

Meaning

+

addition

-

subtraction

*

multiplication

+=

Is equal to itself plus
another variable. E.g.
4+=3+1 is another way of
writing 4=4+3+1

continued


programSeven found on the following
link shows how these operators work in
each calculation near the end.



p=sharing

Data Types


Beginner programmers can confuse
data types with variables because they
are so closely related. Data types are
the kind of data the variable can store.
For instance integers can only store
whole numbers whereas strings can
store letters.



A table of different data types can be
seen below.

Data Types continued
Data Type

Value

int

Whole numbers

floating point

Figures with decimal values

string

Text, an array of chars

char

Single characters of text

boolean

True or false

Selection


Selection is used to determine how a
program should run. One example could
be a program outputting a yes if a value
is lower than 100 or a false if a value is
above 100.



Types of selection include if/else and
switches

Selection continued - if/else


If statements work by using arguments to measure
variables and make decisions based on them.



An example of an if/else statement might be:



If (selection=true)
{
Cout<<“True”<<endl;
}
Else if
{
Cout <<“false”<<endl;
}

Selection continued - if/else


In this scenario selection=true has been used
as the argument to determine how the
selection should be made. If the variable
selection is true then the first if statement is
used and if it not true then the else selection
takes over and outputs „false‟.



An example of an if/else selection in use can
be seen in programSeven through the link:

Selection continued - Switches


Switches work by making a selection from a list of possible cases. This
selection is made by comparing a variable to a list of values. An
example of this might be:
Switch(selection)
{
Case „a‟:
cout<<“a”<<endl;
break;
Case „b‟:
cout<<“b”<<endl;
break;
}

One important thing to note with switches is the break used at the end of
each case, as can be seen above. Without a break to „break out‟ of the
selection the program will carry through all the cases below it. For instance
without a break in case a, case b would be carried out next even though it
was not meant to be.



In that example selection is the variable
being used in the argument and case a
is selected if that is the variable value or
case b if that is. To see a switch in
action please refer to programEight in
the following folder.



p=sharing



When using switches you often rely on user
input and this can lead to problems. With
switches you can make inputs to a char data
type variable however if the user enters
several keystrokes instead of one then the
program will register this as 3 separate entry
and try to go through the menu 3 times.
Something which is not very useful.



If the user also inputs an invalid entry then it
will cause the program to crash. All of which
leads me to my next slide.



Switches can be made much more efficient
by using error validation techniques. One
of these techniques is to simply setup a
default case at the end, much like can be
seen below.

default:
cout << "nCharacter entered was not
an optionn" << endl;
break;

Another method of validation could be input validation. To do this I usually use
a relatively simple if/else statement as can be seen below.



//input validation
if (input.length() == 1)
{
//If the input length is 1 then 'input' which is string is run as an array and the
first letter is
passed to select as its value
select = input[0];
}
else
{
cout << "nCharacter entered was not an optionn" << endl;
//If the validation fails then restart the function
main();
}
To see this code in use please see programEightPartTwo on the following link:
https://drive.google.com/folderview?id=0B7EEqo1krfWPLWJUZXc5RC1tdUU&us
p=sharing

Iteration


Iteration refers to the use of loops.
There are two kinds of loops; while
loops and for loops.



While loops are the simpler of the two
and so I will be starting with them.

Iteration continued


A while loop is a way of telling the compiler „do this while
this argument is true‟ and using code like this:

While(argument)
{
Possible changes to argument
}
A good example of this in use can be found by looking at part
one or part two of programEight. You can see that there is
actually a while loop around almost everything but the
variable declarations.
https://drive.google.com/folderview?id=0B7EEqo1krfWPLWJ
UZXc5RC1tdUU&usp=sharing

Iteration continued


A for loop is a little more complex. Essentially
they work the same as while loops however
within the argument brackets you can declare
variable value, setup an argument for looping
and increment the variable value.



An increment is a way of controlling how many
times a loop is done. If you want something to
be performed 4 times then you can increment
a variable equal to 0 by 1 each loop until it
reaches 4. The loop argument can then be to
stop the loop when the variable reaches 4. In
this way a loop can be made 3 times to give a
total of 4 cycles. An example of this can be
seen on the following slide.

Iteration continued
For (increment=0; increment<5; increment++)
{
cout << “you have looped ” <<
increment << “times” << endl;
}
This simple for loop uses an increment to loop
and to output how many loops have been done
each time. To see this in use please use
programNine in the following link:
https://drive.google.com/folderview?id=0B7EEqo
1krfWPLWJUZXc5RC1tdUU&usp=sharing

Data structure


The term data structure refers to how data is organised into a
related group. Examples of data structures could be arrays,
records or tables but for C++ programming arrays are what I will
be focusing on.



Arrays work by listing a series of values as below.



int array1[N] = {3,6,9,4,7,4,2,2,4,2};



In this case the array1 has been declared as a series of
integers which are declared within squiggly brackets. The N
value in this case represents a number and this number
corresponds to the array value. For instance if N=0 then the
array result would be 3 and if N=2 then the array result would
be 9.



This method is very useful for grouping series of data. An
example of that could be students grades. To see an example of
that in a program please open programTen in
https://drive.google.com/folderview?id=0B7EEqo1krfWPLWJUZ
Xc5RC1tdUU&usp=sharing

Functions


A function is essentially a block of code
which can be given a name and called from
anywhere. Functions are a good way of
reusing code which speeds up coding
considerably.



You declare a function by writing a variable
type, void in the case below as it is not
returning anything, and writing a function
name followed by two brackets. An
example of this can be seen on the next
slide.

Functions continued
void hello()
{
cout << “Hello World” << endl;
}
//The function is then called within another
function like this
hello();

Functions continued


One very important aspect to note with using
functions is that the main() function is always called
first as standard by the compiler and so it is worth
bearing in mind that this should be the main function
where applicable.



() these brackets are always needed and are used to
pass values into a function. The values inside are
called function paramaters. You do not have to use
them however but to pass values for variables from
one function to another without using global
variables they are necessary. The { brackets are
always needed to hold the actual code of the
function.

Functions continued


Function parameters are necessary to send values
of variables from one function to another. Without
them global variables would be necessary and this is
bad practice as with many functions writing and
reading to them it can become very confusing as to
what is actually happening. An example of what this
might look like can be seen below.

int Num1AndNum2(int num1, int num2)
{
return num1 + num2;
}
int Sum = Num1AndNum2(5, 9);

Functions continued


Return values are a method of returning a value of a function so that is can be used in
another function. An example of this could be as below.

using namespace std;
int calculate(int num1,int num2)
{
int calculate;
calculate = num1+num2;
return calculate;
}
int main()
{
cout << calculate(4,5) << endl;
cout << calculate(98,52) << endl;
system("pause");
}
This program can be seen within programEleven in
https://drive.google.com/folderview?id=0B7EEqo1krfWPLWJUZXc5RC1tdUU&usp=sharing

Quiz


A quiz to test your knowledge. Answers
found on next slide.

1. What is a function?
 2. What is an #include directive?
 3. What s the difference between a
variable and an assignment?
 4. What is an iteration?


Answers
1. A function is a grouping of code
accessible anywhere in a program which is
used for reusable code as it can be called
again and again.
 2. An #include directive is a way of
accessing a library which tells the compiler
how to handle things
 3. A variable is a declared entity to store
values. Assignment is the storing of said
values
 4. An iteration is a loop


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