Chapter 2 Introduction to C++

Department of Computer ScienceMissouri 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<iostream>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

CommentsMy:

// 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 inchesint width = 15; // width in inchesint area; // calculated area

// calculate rectangle areaarea = 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<iostream>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 <aFileName>

An example

// This program calculates a pay check.

#include<iostream>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

cout

ostream

……

C++

An example

// This program calculates a pay check.

#include<iostream>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<iostream>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 =

Outputcout<<“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) 13 - 7 ternary (3 operands) exp1 ? exp2 : exp3

Arithmetic Operators

Ternary operator: conditional operatorX<0 ? Y=10 : z=20;

Binary Arithmetic Operators

SYMBOL OPERATION EXAMPLE VALUE 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 integerscout << 13 / 5; // displays 2cout << 91 / 7; // displays 13

If either operand is floating point, the result is floating pointcout << 13 / 5.0; // displays 2.6cout << 91.0 / 7; // displays 13.0

% Operator

% (modulus) operator computes the remainder resulting from integer divisioncout << 13 % 5; // displays 3

% requires integers for both operandscout << 13 % 5.0; // error

An example

// This program calculates a pay check.

#include<iostream>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 ObjectExercise:

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<iostream> 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 <iostream.h>

• Do not use using namespace convention

• May not compile with a standard C++ compiler