1. LESSON 2 Basic of C++

2. Writing the first program
//my first program in C++ #include<iostream> #include<conio.h> using namespace std; int main() { cout<< “Hello World!”; getch(); return 0; }
Hello World!

3. Structure of C++ Program
hash sign
#include <iostream> #include <conio.h> using namespace std; int main() { }
 Preprocessor directives
 Namespace library
 Main function header
brace
 Open the block
 Write declarations and statements
 Close the block
brace

4. Writing the first program
Source Code
//my first program in C++ #include<iostream> #include<conio.h> using namespace std; int main() { cout<< “Hello World!”; getch(); return 0; }

5. Writing the second program
//my second program in C++ #include<iostream> #include<conio.h> using namespace std; int main() { cout<< “Hello World!”; cout<< “I’m a C++ program”; getch(); return 0; }
Hello World! I’m a C++ program
Hello World!

6. Comments
Text that are inserted into the source code to explain what the code is doing.
Two types of comments:
Line comment //
Block comment /* */

7. Comments Example –1 #include<iostream> using namespace std;
int main() {
cout <<"I play Football";
// Abdullah
// ID=3333
return 0; }
Example -2
/* Abdullah
ID =3333 */

8. Program with Comment
//my first program in C++ #include<iostream> #include<conio.h> using namespace std; int main() { cout<< “Multi-line comment”; /*This line is part of the block or multi-line comment. This line is also part of the block comment */ cout<< “Line comment 1”; //This line comment takes up an entire line. cout<< “Line comment 2”; getch(); return 0; }
Multi-line comment Line Comment1 Line comment2
Multi-line comment
Multi-line comment Line Comment1

9. endl Command
#include<iostream> #include<conio.h> using namespace std; int main() { cout<< “Hello”; cout<< “How are you.”; cout<< “What is your name?”; getch(); return 0; }
Hello How are you. What is your name?
Hello
Hello How are you.

10. endl Command
#include<iostream> #include<conio.h> using namespace std; int main() { cout<< “Hello” << endl; cout<< “How are you.” << endl; cout<< “What is your name?” << endl; getch(); return 0; }
Hello
How are you.
What is your name?
Hello
Hello
How are you.

11. Variables
A named memory location where the value is stored.

12. Format to Declare a Variable
Data Type
int height;
user defined Variable Name based on the naming RULES.

13. Rules in Naming Variables
Variables may consist of letters, digits and underscore ( _ ) character with the following condition:
They must begin either with a letter or an underscore.
Special symbols are not allowed
Space is not allowed
Reserved words (Keywords) are not allowed

14. Reserved Words

15. Sample

16. Valid/Invalid Variable Names
John
int
letter
try
char a
s_name
my_first_name
_name
First*name
1man
first name
@name
v.a.l.u.e

17. Data Types Specific category of information that a variable contains.
Description
int
Store numeric integer values
float
Numeric values with fractional parts
char
Store one character
void
Return null or valueless
string
Store many characters

18. Literals int float char string void -259 -13 200 -6.16 -4.4 2.7541
200
float
-6.16
-4.4
2.7541
10.5
char
‘z’
‘p’
‘x’
‘a’
string
“Hello World”
“How do you do?”
“Ali”
“Diploma 1”
void
null

19. Declaration Statement - Example
int sum; char gender; double studentgpa;
int a,b,c;
int a;
int b;
int c;
int num = 15;
float grade1=81.0;

20. Operating with variables
#include <iostream>
#include <conio.h>
using namespace std;
int main() {
int a,b;
int result;
a=5;
b=2;
a=a+1;
result = a–b;
cout <<“Result equals to”<<result;
getch();
return 0; } a 6 a 5 a 2 b b
result 4
result
Result equals to 4

21. Constants Literal Symbolic Memory Expression with a fixed value.
Ways to use constants:
Literal
Symbolic
Memory
float pi=3.1416;
#define pi ;
const double pi=3.1416;

22. Operating with const #include <iostream> raduis=20;
#include <conio.h>
using namespace std;
int main() {
const float PI=3.1416;
float radius=5;
float area;
area=radius*radius*PI;
cout<<“The area is”<<area
<<“with a radius of 5.\n”;
raduis=20;
area=radius*radius*PI;
cout <<“The area is ”<<area
<<“with a radius of 20.\n”;
getch();
return 0; }
The area is with the radius of 5.
The area is with the radius of 20.
The area is with the radius of 5.

23. Operating with const #include <iostream> raduis=20;
#include <conio.h>
#define PI ;
using namespace std;
int main() {
float radius=5;
float area;
area=radius*radius*PI;
cout<<“The area is”<<area
<<“with a radius of 5.\n”;
raduis=20;
area=radius*radius*PI;
cout <<“The area is ”<<area
<<“with a radius of 20.\n”;
getch();
return 0; }
The area is with the radius of 5.
The area is with the radius of 20.
The area is with the radius of 5.

24. cout
is output command that sends data given to it to the standard output device.

25. Operating with cout #include <iostream> #include <conio.h>
using namespace std;
int main() {
int a,b;
float x,y;
a=10;
b=20;
x= ;
y = ;
cout <<“a=”<<a
<<“, b=”<<b
<<“, x=”<<x
<<“, y=”<<y;
getch();
return 0; } 10 a a 20 b b x x y y
A=10, b=20, x= , y=

26. cin Command reads in information from the keyboard. int age;
cin >> age;
float salary;
cin >> salary;

27. Operating with cin #include <iostream> #include <conio.h>
using namespace std;
int main() {
int number;
cout<<“Enter number: ”
cin>> number;
cout>>”You entered ” number;
getch();
return 0; } 27
number
number
Enter number: 27
You have entered 27
Enter number:
Enter number: 27

28. Backup Slides

29. Comments Line comment Sample 1 Sample 2
cout << “Hello world!” <<endl; //Everything from here to the right is ignored
Sample 2
cout << “Hello world!” <<endl; //cout and endl live in the iostream library
cout << “It is nice to meet you” <<endl; //this code is hard to read
cout << “Yeah!” <<endl; //specially when lines are different length

30. Comments Sample 3 //cout and endl live in the iostream library
cout << “Hello world!” <<endl;
//this code is easir to read
cout << “It is nice to meet you” <<endl;
//don’t you think so?
cout << “Yeah!” <<endl;

31. Comments Multi-line Comment Sample 1 Sample 2
/* This is a multi-line comment
This line will be ignored.
so will this one. */
Sample 2
/* This is a multi-line comment.
* the matching asterisks to the left
* can make this easier to read */