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COM1100 Fundamentals of Computer Science –Winter 2000 Lecture 4 01/13/99

Last lecture Identifier Variable declare and use Assignment statements Basic Data Type int double char

Today’s lecture Arithmetic operations Safe I /O operations Visual C++ IDE Graphic functions Examples

Arithmetic Operations Integer(int) and real number(double) can be added, subtracted, multiplied, and divided. The operators used for arithmetic operations are called arithmetic operators. Addition + Subtraction - Multiplication * Division / Modulus Division %

Integer Division In C++, the fractional part of the result obtained when dividing two integers is dropped(truncated) 15 / 2 = 7  // instead of 7.5 15.0 / 2 = 7.5 15 / 2.0 = 7.5 Modulus Operator (%) : capture the remainder of an integer division  9 % 4 = 1 17 % 3 = 2 14 % 2 = 0 The Modulus Operator can be used only with integers

Rules of expressions -- 1 C++ requires certain rules be followed when writing arithmetic expressions containing more than one operators Two binary arithmetic operator symbols must never be placed side by side 5 * % 6  // Wrong ! Parentheses should be used to form grouping and all expressions enclosed within parentheses are evaluated first. ( 6 + 4 ) / ( 2 + 3 ) = 10 / 5    = 2

Rules of expressions -- 2 Sets of parentheses may also be enclosed by other parentheses and expressions in the innermost parentheses are always evaluated first. (2 * (3 + 7) ) / 5   = ( 2 * 10 ) / 5   = 20 / 5   = 4 Parentheses can not be used to indicate multiplication ( 3 + 4 ) ( 5 + 1)  // Wrong ! ( 3 + 4 ) * ( 5 + 1)  // OK !

Operator Precedence & Associativity In the absence of parentheses, expressions containing multiple operators evaluated by the priority, or precedence, of the operators (high->low) Unary – * / % left to right + - left to right Example 8 + 5 * 7 % 2 * 4   = 8 + 35 % 2 * 4   = 8 + 1 * 4 = 8 + 4 = 12

Microsoft Visual C++ 6.0 IDE ·        Microsoft Visual C++ 6.0 with its Integrated Development Environment ( IDE ) is a part of the Visual Studio 98 suite of development tools. ·        Visual Studio 98 also includes Visual Basic, Visual J++, and a development tool for FoxPro database programs. ·        Visual C++, Visual Basic and Visual J++ each have their own distinct IDE. ·        Visual Studio simplifies the care and feeding of projects.

Visual C++ Projects --1 All applications developed using IDE are maintained as project workspaces. A workspace can contain multiple projects, but usually does not. Thus, we will use the terms workspace and project interchangeably. In Visual C++, even simply programs consisting of one source code file are maintained as project.

Visual C++ Projects --2 A project consists of a number of files. Some of them are created and maintained by the IDE, and others are developed and maintained by the programmer. .cpp ( source code file) .dsp ( project file) .dsw ( workspace file) .ncb ( supports ClassView) .opt ( contains workspace configuration) .plg ( log file of the build process)

VC++ IDE -- Workspace window Workspace window  -- This window displays information about the workspace that is currently open. Included are pages for the ClassView, the FileView, and the ResourceView, which permits one to navigate through the project contents from a class, file, and a resource point of view, respectively.

VC++ IDE -- Editor window Editor window -- This window provides a color-coded editor for source code and a WYSIWYG editor for application resource, such as menus, dialogs, and bitmaps.

VC++ IDE -- Tool bars & Output Windows Tool bars – These bars provide shortcuts to a variety of tasks that one perform while building an application. The bars can be customized completely. Output window – This window displays output information from various operations. The most common use for this window is to view complier and linker messages.

How to run course VC++ project at home ? Install VC++ 6.0 Download and Install Visual studio service pack 3 Download and install Winzip 7.0 Download a shell project from www.ccs.neu.edu/course/com1100/Resource ShellProject.exe builds a Shell project ready to be used to make new project. It is a self-extracting archive and should be expanded in the folder where you want the work to go. Accept the suggestion to put the files in the specified folders.

Safe Input operations Raw input Verified input Verified Input with Default

Raw input The built-in input functions/statements in most programming languages support this mode of input. cin >> Example int x; cout << “Please enter a number : “ ; cin >> x; // what happened if I enter a letter instead of a number cout << “The number you entered is : “ << x << endl;

Raw input – Example 2 string myName;    cout << “Please enter your name : “ ;    cin >> myName;    // what happened if I enter a number instead of a string   // what happened if I enter : Elice Brown   cout << “The name entered is : “ << myName << endl ;

Verified input It is not part of C++. It is developed by Prof. Rasala int x;    x = RequestInt(“Please enter a number :"); Double y;   y = RequestDouble(“Please enter a real num :"); String myName; RequestString(“Enter your name: ”,myName);

Verified Input with Default The only difference from the verified input is that the program supplies a default value. The default value is displayed after the prompt, to alert the user to its availability and to inform the user of the default value. The statements have the format: x = RequestInt(“Enter a number:", 3); RequestString("Type in your name", “Yuhong”, myName);

Summary of input -- 1 Raw Read provides no error checking. Two statements are needed - an output statement that prints the prompt to the user and a basic input statement. int x; cout << “Please enter a number : ”; cin >> x;

Summary of input -- 2 Verified Read is uses a function that prints the given prompt, reads the input, and verifies that the input is of correct type. It repeats the request for input until valid input is supplied. int x; x = RequestInt(“Please enter a number :”);

Summary of input -- 3 Verified Read with Default uses a function that prints the given prompt as well as the given default value and awaits input. If the input is not correct, the function repeats the request and gives the user another chance to type in the data. If the user enters no data, the default value is used instead. int x; x = RequestInt(“Enter a number:”, 3);

Coordinate  system It is a left-handed coordinate system. What this means is that the origin of the screen lies at the upper left corner. The Y axis increases towards the bottom of the screen, the X axis increases towards the right.

Coordinate system -- example

Graphic functions SetForeColor(R,G,B); SetForeColor(255,0,0);  // red SetForeColor(0,255,0);  // green SetForeColor(0,0,255);  // blue  PaintRect(left,top,right,bottom); PaintRect(10,10,100,100) PaintCircle(xcenter,ycenter,radius); PaintCircle(200,200,10) PaintOval(left,top,right,bottom); InvertOval(left,top,right,bottom);

Today’s lecture Arithmetic operations Safe I /O operations Visual C++ IDE Graphic functions Examples

Lecture next week Functions Safe I /O operations More Graphic functions