1. Lecture 1B Introduction Richard Gesick
Figures from Lewis, “C# Software Solutions”, Addison Wesley

2. Agenda Overview of Programming Languages Basics of C++ and the IDE
Errors
Intro to Objects and Classes

3. Programming Languages
A programming language specifies the words and symbols that we can use to write a program
A programming language employs a set of rules that dictate how the words and symbols can be put together to form valid program statements

4. Programming Languages
Machine language
Assembly language
High-level languages

5. Machine & Assembly Languages
Machine language
Written in binary or hex
Written using CPU instruction set
Difficult to write, and not portable
Assembly language
Written using mnemonics for instructions and symbolic names for variables
Assembler converts code to machine language
Easier to write, but still not portable
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6. High-Level Languages Examples: Fortran, Perl, COBOL, C++, Java
Highly symbolic
Portable among CPU architectures
Languages can be designed for specific uses:
Perl: Internet applications
Fortran: scientific applications
COBOL: business applications

7. High-Level Languages Compiled Interpreted
Compiler converts source code (instructions and data) into machine language, then program is executed
Interpreted
Interpreter converts instructions into machine language at run time as instructions are executed
Usually executes more slowly than compiled program

8. Building a Program

9. 1-9

10. Programming Basics
Programming is translating a problem into ordered steps consisting of operations a computer can perform:
Input
Calculations
Comparisons of values
Moving data
Output
The order of execution of instructions is called flow of control

11. Four Types of Flow of Control
Sequential Processing
Execute instructions in order
Function Call
Jump to code in method, then return
Selection
Choose code to execute based on data value
Looping or Iteration
Repeat operations for multiple data values

12. Program Development
The mechanics of developing a program include several activities
writing the program in a specific programming language
translating the program into a form that the computer can execute
investigating and fixing various types of errors that can occur
Software tools can be used to help with all parts of this process

13. Problem Solving The purpose of writing a program is to solve a problem
Solving a problem consists of multiple activities:
Understand the problem
Design a solution
Consider alternatives and refine the solution
Implement the solution
Test the solution
These activities are not purely linear – they overlap and interact

14. Problem Solving
The key to designing a solution is breaking it down into manageable pieces
When writing software, we design separate pieces that are responsible for certain parts of the solution
An object-oriented approach lends itself to this kind of solution decomposition
We will dissect our solutions into pieces called objects and classes

15. Program Skeleton
#include "stdafx.h" #include <string> #include <iostream> using namespace std; int _tmain(int argc, _TCHAR* argv[]) { cout<<"hello world\n"; cout<<"enter your name"; string name; getline(cin,name); cout<<"Hello "<<name<<endl; return 0; }

16. Preprocessor directives
#include <iostream> // Required for cout, endl.
#include <cmath> // Required for sqrt()
#include <string> //Required for strings
Give instructions to the preprocessor before the program is compiled.
Begin with #
#include directives ‘add’ or ‘insert’ the named files (and the functionality defined in the files)into the program

17. Using directives using namespace std;
Tell the compiler to use the library names declared in the namespace.
The ‘std’, or standard namespace contains C++ language-defined components.

18. Main function header int _tmain(int argc, _TCHAR* argv[])
Defines the starting point (i.e. entry point) for a C++ program
The keyword ‘int’ indicates that the function will return an integer value to the system when the function completes

19. Code blocks
are zero or more C++ declarations or statements enclosed by curly brackets { }
The code that defines what a function does (in this case, the main function of the program) is often defined in a code block following the header.

21. Identifiers Words in programs Categories: We make up Others make up
Reserved in the language

22. C++ Identifiers
Must begin with an alphabetic character or the underscore character ‘_’
Alphabetic characters may be either upper or lower case.
C++ is CASE SENSITIVE, so ‘a’ != ‘A’, etc…
May contain digits, but not in as the first character.
May be of any length, but the first 31 characters must be unique.
May NOT be C++ keywords.

23. C++ Identifiers
Should be carefully chosen to reflect the contents of the object.
The name should also reflect the units of measurements when applicable.
Must be declared (and therefore typed) before they may be used.
C++ is a strongly typed programming language.

24. C++ Keywords

25. Initial Values C++ does not provide initial values for variables.
Thus using the value of a variable before it is initialized may result in ‘garbage’.

26. White Space Spaces, blank lines, and tabs are called white space
White space is used to separate words and symbols in a program
Extra white space is ignored
A valid C++ program can be formatted many ways
Programs should be formatted to enhance readability, using consistent indentation

27. Comments Comments in a program are called inline documentation
They should be included to explain the purpose of the program and describe processing steps
They do not affect how a program works
C++ comments can take two forms:
// this comment runs to the end of the line
/* this comment runs to the terminating
symbol, even across line breaks */

28. Syntax and Semantics
The syntax rules of a language define how we can put together symbols, reserved words, and identifiers to make a valid program
The semantics of a program statement define what that statement means (its purpose or role in a program)
A program that is syntactically correct is not necessarily logically (semantically) correct
A program will always do what we tell it to do, not what we meant to tell it to do

29. Errors A program can have four types of errors
The compiler will find syntax errors and other basic problems (compile-time errors)
Mistakes with the language.
Always reported by the compiler
If compile-time errors exist, an executable version of the program is not created

30. Errors
Linking Errors
Missing pieces prevent the final assembly of an executable program
A problem can occur during program execution, such as trying to divide by zero, which causes a program to terminate abnormally (run-time errors)

31. Logic Errors
A program may run, but produce incorrect results, perhaps using an incorrect formula (logical errors)
Can be difficult to find.
It is important to carefully check the output of your programs for errors.
Even programs that appear to work correctly may have bugs!

32. Expect Errors
Process of eliminating logic errors (i.e. bugs) from programs.
User-friendly programming environments such as Microsoft Visual C++ integrate the compiler with
text processors and code editors
special tools to help find bugs in programs (debugger)
testing tools
and much more…

33. Program Structure In the C++ programming language:
A program is made up of one or more classes
A class contains one or more methods
A method contains program statements
These terms will be explored in detail throughout the course
An application always contains a method called Main

34. C++ Classes Class Objects
tool for encapsulating data and operations (methods) into one package
defines a template or model for creating and manipulating objects
Objects
data created using the class and its methods
an object is an instance of the class
creating an object is instantiation

35. Multiple objects from the same class

36. Class Declarations Specify a programmer-defined type/object.
Begin with keyword ‘class’ followed by the name (i.e. identifier) of the type.
Class definition is made in a code block.
Class members may include data (attributes) and methods (functions).
Visibilities of public, protected, and private are used to control access to class members
A semicolon must follow the closing bracket };
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37. Class Methods
Define the operations that can be performed on class objects.
A constructor is a special method that is executed when objects of the class type are created (instantiated).
Constructors must have the same name as the class.
A class may define multiple constructors to allow greater flexibility in creating objects.
The default constructor is the one that has no parameters.
Parameterized constructors provide initial values of data members.
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38. Class Definitions Often declared in two parts:
The class declaration is typically written in a file named ‘className.h’
Defines the class including data members and the headers of the class methods.
The implementation of class methods is typically written in a file named ‘className.cpp’
#include “className.h”
Provides implementations for all class methods.
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39. Class Syntax
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40. Using a Class
Once a class is defined, you may use the class as a type specifier.
You must include the class definition (i.e. header file)
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41. Objects
An object has:
state - descriptive characteristics
behaviors - what it can do (or what can be done to it)
The state of a bank account includes its current balance
The behaviors associated with a bank account include the ability to make deposits and withdrawals
Note that the behavior of an object might change its state

42. Objects and Classes A class An object (the concept) (the realization)
Bank Account
A class
(the concept)
John’s Bank Account
Balance: $5,257
An object
(the realization)
Bill’s Bank Account
Balance: $1,245,069
Mary’s Bank Account
Balance: $16,833
Multiple objects
from the same class

43. Class and Object Example
How would you describe or define these pictures?
What are the differences?
What are the similarities?
Are you describing a single entity or an entire group of entities?