Chapter 2 Introduction to C++ Department of Computer Science Missouri State University

Outline  The structure of C++ programs  Cout Objects  The #include directive  Variables and constants  Data Types  Operations  Comments  Programming Style

An example // This program calculates a pay check. #include using namespace std; void main( ) { int workerPayRate; float workHours, pay; workerPayRate=12; workHours=10.5; pay=workHours  workerPayRate; cout<<“A worker earns $”<<pay<<endl; }

Comments  Used to document parts of the program  Intended for persons reading the source code of the program: Indicate the purpose of the program Describe the use of variables Explain complex sections of code  Are ignored by the compiler

Comments My: // all students grades statistics void main( ) { } Linda: // freshman grades statistics void main( ) { } David: // sophomore grades statistics void main( ) { } Kevins: // junior grades statistics void main( ) { }

C++ Style Comments Begin with // through to the end of line: int length = 12; // length in inches int width = 15; // width in inches int area; // calculated area // calculate rectangle area area = length * width;

C-Style Comments  Begin with /*, end with */  Can span multiple lines: /* this is a multi-line C-style comment */  Can be used like C++ style comments: int area; /* calculated area */

An example // This program calculates a pay check. #include using namespace std; void main( ) { int workerPayRate; float workHours, pay; workerPayRate=12; workHours=10.5; pay=workHours  workerPayRate; cout<<“A worker earns $”<<pay<<endl; }

Preprocessor Directive Part  # include

An example // This program calculates a pay check. #include using namespace std; void main( ) { int workerPayRate; float workHours, pay; workerPayRate=12; workHours=10.5; pay=workHours  workerPayRate; cout<<“A worker earns $”<<pay<<endl; }

Namespaces Cheek  Glass  Temple Missouri State Campus cou t ostrea m  …… C++

An example // This program calculates a pay check. #include using namespace std; void main( ) { int workerPayRate; float workHours, pay; workerPayRate=12; workHours=10.5; pay=workHours  workerPayRate; cout<<“A worker earns $”<<pay<<endl; }

Procedure Part  General form of a procedure or a function Return _Type functioName ( parameter list) { Function_body }

An example // This program calculates a pay check. #include using namespace std; void main( ) { int workerPayRate; float workHours, pay; workerPayRate=12; workHours=10.5; pay=workHours  workerPayRate; cout<<“A worker earns $”<<pay<<endl; }

Operations : Assignment float currentTemperature; double pi; int Price; currentTemperature = pi = Price = Output cout<<“Current temperature is “ <<currentTemperature<<endl; cout<<“pi=”<<pi<<endl;

Arithmetic Operators  Used for performing numeric calculations  C++ has unary, binary, and ternary operators: unary (1 operand) -5 binary (2 operands) ternary (3 operands) exp1 ? exp2 : exp3

Arithmetic Operators  Ternary operator: conditional operator X<0 ? Y=10 : z=20;

Binary Arithmetic Operators SYMBOLOPERATIONEXAMPLEVALUE OF ans + addition ans = 7 + 3;10 - subtraction ans = 7 - 3;4 * multiplication ans = 7 * 3;21 / division ans = 7 / 3;2 % modulus ans = 7 % 3;1

/ Operator  / (division) operator performs integer division if both operands are integers cout << 13 / 5; // displays 2 cout << 91 / 7; // displays 13  If either operand is floating point, the result is floating point cout << 13 / 5.0; // displays 2.6 cout << 91.0 / 7; // displays 13.0

% Operator  % (modulus) operator computes the remainder resulting from integer division cout << 13 % 5; // displays 3  % requires integers for both operands cout << 13 % 5.0; // error

An example // This program calculates a pay check. #include using namespace std; void main( ) { int workerPayRate; float workHours, pay; workerPayRate=12; workHours=10.5; pay=workHours  workerPayRate; cout<<“A worker earns $”<<pay<<endl; }

Cout Object Exercise: 1) cout<<“You got 98 points. Cheers!”; 2) cout<<“You got ”; cout<<“98”; cout<<“ points. ”; cout<<“Cheers!”; 3) cout<<“You got ”<<“98” <<“ ponts. ”<<“Cheers!”; 4) cout<<“You got ”<<98<<“ points. Cheers!”; 5) cout<<“You got ”<<98<<“ points.”<<endl; cout<<“Cheers!”;

Common escape sequences  Exercise 1 He says “I’m genius!”  Exercise 2 My hw is in the directory \upload\csc125\hl

Programming Style  The visual organization of the source code  Includes the use of spaces, tabs, and blank lines  Does not affect the syntax of the program  Affects the readability of the source code

Programming Style // This program calculates a pay check. #include using namespace std; void main ( ){ int workerPayRate; float workHours, pay;workerPayRate=12;workHours=10.5; pay=workHours  workerPayRate; cout<< “A worker earns $”<<pay<<endl; }

Programming Style void main( ) { float height=4, width=3.5, radius=12.1, base=9, top=5.2; float area1, area2, area3, area4; area1=height  width; area2=3.14  radius  radius; area3=height  base/2; area4=(top+base)  width/2; cout<<“Areas:”<<area1<<“, ”<<area2<<“, ” <<area3<<“, ”<<area4<<endl; }

Programming Style Common elements to improve readability:  Braces { } aligned vertically  Indentation of statements within a set of braces  Blank lines between declaration and other statements  Long statements wrapped over multiple lines with aligned operators

Standard and Prestandard C++ Older-style C++ programs: Use.h at end of header files: #include Do not use using namespace convention May not compile with a standard C++ compiler