C++ Chapter I

Chapter I

1

Lecturer: Hong Mom

Objec&ve

Create by: Hong Mom 2

A9er comple;ng this chapter, you will be able to: •  Demonstrate structure of C++ •  Use Input & output stream •  Use comment, Data types , Operators, and Func;on Manipula;ons

Agenda

•  History of C++ •  Structure of C++ language •  Variable Declara;on •  Data types •  Input & Output stream •  Comment •  Operators •  Func;on Manipula;ons


History of C++ •  Evolved from two other language : BCPL and B •  Extension of C •  C++ developed by Bjarne Stroustrup at AT&T Bell Labs in the 1980s.

•  Provides capabili;es for object-‐oriented programming

•  Objects: reusable so9ware components – Model items in real world

•  Object-‐oriented programs – Easy to understand, correct and modify


General form of C++ program

General Form Header File Global Declara;on; int main(){ Local Declara;on; statement(s); return 0; }


Variable •  C++ variable can hold value as

–  Number –  Data (of other type )

•  Variable are memory loca;on •  Name of variable is called iden;fier Example: int age;

double num_dollars; num_dollars = 50.0;


Variable Declara;on

A variable can be given any name, called an iden;fier in C++, provided it is within the following rules:


S  can only be constructed using leeers, numerals or underscored(_)

S  Must start with a leeer or an underscore

S  Cannot be a C++ keyword

S  Can contain any number of characters, but only the first thirty-‐one characters are significant to the C++ compiler

Variable Declara;on

Examples

–  valid identifiers: first_name, age, y1000,salary

–  Invalid identifiers: 100y,*Recle,int


Data types

Type Mem. Used Size Range Precision

int 2 bytes -‐32,768 to 32767 N/A

long (long int) 4 bytes -‐2,147,483,647 to 2,147,483,647

N/A

float 4 bytes ~ 10-‐38 to 1038 7 digits

double 8 bytes ~ 10-‐308 to 10308 15 digits

long double 10 bytes ~ 10 -‐4932 to 104932 19 digits


Some number of types

Data type •  char : holds any single character on the keyboard. •  String : holds more than one character (will learn later) Example: //define variable a as integer int a; //define variable b as boolean bool b; //define variable f as double double f;


// Program to display the memory required by C++ data types. #include<iostream.h> void main() { cout << ” Data type Size (bytes)” <<endl; cout <<” -‐ -‐ -‐ -‐ -‐ -‐ -‐ -‐-‐ -‐ -‐-‐ -‐-‐ -‐ -‐ -‐ -‐ -‐ -‐ -‐“ <<endl; cout <<” char “ << sizeof ( char ) <<endl; cout <<” int “ << sizeof (int ) <<endl; cout <<” long int “ << sizeof ( long ) <<endl; cout <<” bool “ << sizeof ( bool ) <<endl; cout <<” float “ << sizeof (float ) <<endl; cout <<” double “ << sizeof (double ) <<endl; }


Input & Output Stream

•  stream : is a transfer of informa;on in the form of a sequence of bytes

•  iostream library: <iostream.h>: contains cin, cout, cerr, and clog objects •  << and >> : inser;on and extrac;on operators •  cin

•  Standard input (keyboard) •  istream object


Example: cin>>age;

Input & Output Stream •  cout

•  Standard output(display screen) •  ostream object

•  cerr – Outputs immediately – Unbuffered

•  clog –  buffered-‐ prinr when buffer full or flushed


Example: cerr<< something;

Example: clog<< something;

Example: cout<<“CIEDC”;

Input & Output Stream

Example: //test01.cpp // Output a string using cout using std::cout; void main() {

cout << “Welcome to C++ Programming!”; }


// test02.cpp //calcula;ng the sum of two numbers //with using cin and cout #include <iostream> using std::cout; using std::cin; int main(){

int a, b; cout << “Enter two in numbers:”; cin >> a >> b; cout << “sum of “ << a “ and “ << b <<“ is:” <<(a+b) << endl; return 0;

}


Example #include <iostream> using namespace std; int main( ) { char str[] = "Unable to read....";

cerr << "Error message : " << str << endl; return 0;

} When the above code is compiled and executed, it produces following result: Error message : Unable to read....


Example

#include <iostream> using namespace std; int main( ) { char str[] = "Unable to read...."; clog << "Error message : " << str << endl;

return 0; } When the above code is compiled and executed, it produces following result: Error message : Unable to read....


Comments

•  Comment appear in green in C++ •  Comments are explanatory notes; they are ignored by the compiler.

•  Document programs •  Improve program readability.


Comments •  There are two ways to include comments in a program:

–  Single-‐line comment Begin with //

–  Mul;-‐lines comment /*…. */ // A double slash marks the start of a //single line comment.

/* A slash followed by an asterisk marks the start of a multiple line comment. It ends with an asterisk followed by a slash. */


Operator

Binary Operators Symbol Example

Addi;on + c = a+b

Subtrac;on -‐ c = a – b;

Mul;plica;on * c = a * b;

Division / c = a / b;


•  Arithme&c Operator

Operator

Operator Meaning a++ a = a+1; //add by 1 a9er a is used ++a a = a+1; //add by 1 before a is used a-‐-‐ a = a – 1; //sub by 1 a9er a is used -‐-‐a a = a-‐1; //sub by 1 before is used


•  Unary Operator

Operator

Example: cout << “20 divided by 3 is “ << (20/3) << endl; cout <<“With a remainder of “ << (20%3) << endl; Output:

20 divided by 3 is 6 With a remainder of 2


•  The % Operator

Combined Operators

Operators Example

+= c += a ó c = c + a

-‐= c -‐= a ó c = c -‐ a

*= c *= a ó c = c*a

/= c /= a ó c = c / a

%= c %= a ó c = c%a


A statement such as var = var + 3 may also writen as var += 3;

Precedence Rule and Parentheses •  Consider the following statement

var = 2 + 6 * 9 ; Does this mean (a) that 2 is added to 6, giving 8, which is mul;plied by 9, Giving var a value of 72 (b) that 6 is mul;plied by 9, which is added to 2, giving var a value of 56 (a) and (b) ,which one is right answer?


Precedence Rule and Parentheses

Operator Precedence Meaning Associa&vity -‐ Highest Unary minus Right to le9 * / %

Lower Mul;plica;on, Division, and modulus

Le9 to right

+ -‐

Lowest Addi;on and subtrac;on

Le9 to right


Operator precedence provide these rules.

Notes: you can use parentheses to change the order of evalua;on Ex: var = ( 2 + 6 ) * 9;

Manipulators

•  Manipulators are used to modify input and output data stream.

•  #include <iomanip> •  Manipulators

-‐ endl: used in previous program to skip to the start of a new line On the screen. -‐ setw: used to set the width of a data field.


Manipulators Example: #include<iostream> #include<iomanip> void main(){

int num1 = 111, num2 = 2345; cout << “Without setw:” << endl; cout << num1 << num2 << endl; cout << “With setw:” << endl; cout << setw(4) << num1

<< setw(7) << num2 << endl; } Create by: Hong Mom 27

Output:

Without setw:

1112345

With setw:

111 2345

Manipulators -‐ sePill: used to change the “padding” character from a space to any other character. Example: long num = 123456; cout << setw(9) << sePill(‘*’) << num << endl; cout << setw(10) << sePill(‘0’) << num << endl;

Output: ***123456 0000123456


Manipulators

-‐ setprecision: used to specify the number of digits of a number to display. Example: double num = 123.4567; cout << num << endl; cout << setprecision(7) << num << endl; cout << fixed << setprecision (2) << num << endl;


Output: 123.456 123.4567 123.45

Documents

C++ Chapter I