Transcript Lecture 13 Slides

Programming for Beginners
Lecture 13: An Introduction to C++
Martin Nelson
Elizabeth FitzGerald
Session 13 – aims and objectives

So far we’ve only talked about Java, but there are many
other languages available...

Today, we will take a quick look at one alternative: C++.

We will see that C++ has many similarities to Java.

There are also many key differences.
Languages Available

So far, we’ve only talked about Java, but there are many
other languages available...
Procedural


Fortran
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COBOL (old versions)
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Pascal
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C
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Perl
Object-oriented
 COBOL (latest version)
 C++
 C#
 Java
 Delphi
 Visual Basic
 Perl
Language choice depends on the task in hand!
Languages Available

Fortran (acronym for formula translator) is one of the
oldest high-level languages. It is still commonly used for
mathematical/scientific computation.

COBOL (Common business-oriented language) is another
old high-level language. Some argue that it is now very
out-dated. Was used for business applications running on
large computers. Required very wordy coding!

Pascal – often used for teaching, but not much else.
Very inflexible.

Perl (Practical Extraction & Report Language) is a
programming language especially designed for processing
text. Good for quick program development, task
automation and some web applications.
C
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Procedural language

Originally designed as a systems programming language –
e.g. Unix.

Can be used for a variety of applications, from business
programs to engineering.

Requires less memory than other languages.
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Lower-level, a lot closer to assembly language than other
high-level languages

this can make it unsuitable for some applications – especially
those requiring rapid development.
C++

C, but incremented once!

Includes object-orientation, but can still use procedural
syntax too.

Popular for writing programs for graphical applications,
such as Windows or Mac applications

Good general language to learn, especially if you want a
job as a programmer!
C#

Hybrid of C and C++, written by Microsoft to compete
with Java.

Object-oriented programming language used with XMLbased web services on the .NET platform.


We’ll talk about XML next time...
The .NET framework allows interaction between codes written in
different languages.

Designed for improving productivity in the development of
web applications.
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Many similarities to Java!
Differences between C and C++
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C++ is object-oriented; C is not
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C++ standardizes how objects are created and managed;
C is a lot more variable in terms of style and design.
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C++ applications are slower at runtime and slower to
compile than C programs.

C++ programs tend to be larger than C.
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C interacts with memory much more than C++ (pointers).
Compiling C++ Code on Granby
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Various C++ compilers are available. We will use g++
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C++ files are usually given the extension .cpp
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To compile the file test.cpp:
g++ test.cpp
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By default, the compiler will create an executable called
a.out. To run it, type
./a.out

Or, we can give the output a specific name (test):
g++ -o test test.cpp
./test
Compiling C++ Code on Granby

Various C++ compilers are available. We will use g++

C++ files are usually given the extension .cpp

To compile the file test.cpp:
g++ test.cpp

By default, the compiler will create an executable called
a.out. To run it, type
Input file name
./a.out

Or, we can give the output a specific name (test):
g++ -o test test.cpp
./test
Output file name
Hello World
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Typical beginner’s program

Used as first exposure to a new programming language or
environment
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Can be written in loads of different languages:
http://www2.latech.edu/~acm/HelloWorld.html
(lists 204 examples of different Hello World
programs!)
Hello World in Java
class Hello
{
public static void main (String[] args);
{
System.out.print("Hello World");
}
}
Hello World in C
#include <stdio.h>
Header file providing
the printf method
main()
{
printf ("Hello World!\n");
}

Just as in Java, every C program has a method called
main, which is run when the program starts.
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The printf method is used to write some text on the
screen.
Hello World in C++
#include <iostream>
Provides cout
using namespace std;
Don’t worry about
this yet!
In C++, main must return an int.
int main()
{
cout << “Hello World!\n";
return 0;
}
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In C++, cout represents the standard output stream (the
screen.
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The operator << can be read as “send to”.
User Input in C++
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Just as cout is the standard output stream (the screen),
we have cin to represent the standard input (the
keyboard).
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The operator >> means “read from”.
User Input in C++
#include <iostream>
Provides cout & cin
#include <string>
using namespace std;
int main()
Provides the string class
Declare a string
{
string name;
cout <<“Tell me your name!” << endl;
cin >> name;
cout << “Hello “ << name << endl;
return 0;
}
Newline
Flow Control in C++

For loop:
for( int i=1; i<100; i++)
{
cout << i << endl;
}
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While loop:
int i=100;
while(i>0)
{
cout << i << endl;
i--;
}
Flow Control in C++

If statement:
int score;
cout << “Enter your exam mark” << endl;
cin >> score;
if(score<40)
{
cout << “You failed!” << endl;
}
else
{
cout << “You passed!” << endl;
}
Arrays in C++
double nums[3];
nums[0] = 1;
nums[1] = 12;
nums[2] = 428;
Declare an array
Assign values
double total = nums[0]+nums[1]+nums[2];
cout << “Total is “ << total << endl;

Beware: C++ will let you refer to nums[3] in the above,
but that data will rarely make sense and is likely to make
your code malfunction.
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Can also have arrays of arrays! e.g. nums[4][5]
Methods in C++
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Easiest way (for now) is to define methods above main.
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Can also define methods below main, or in separate files,
but this is harder. We’ll ignore these options for now.
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Just like Java, methods have a return type and
(optionally) a list of arguments.
Methods in C++
#include <iostream>
using namespace std;
// Method to add two numbers together
double add(double a, double b)
{
return a+b;
}
int main()
{
cout << add(1,3) << endl;
return 0;
}
Want to know more about C++?
if(answer==no)
{
Stop listening for a minute!
}
else
{
Sign up for the forthcoming C++ course!
}

C++ Programming
Ten Sessions: 12th April – 17th May 2011
Tutor: Dr. Robert Oates ([email protected])
More info: www.nottingham.ac.uk/csc
Exercises
Choice of exercises for today:

Either have a go at some new exercises, which introduce
some familiar concepts in C++.
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Or, continue with your Java Address Book.
Coming up in Session 14
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An introduction to scripting languages
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HTML

CSS
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XML/XSLT
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php
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javascript