Lecture# 3 Programming Concepts

1. Lecture# 3 Programming Concepts

2. In Last Lecture • First Program • Programs consists of Blocks(Functions) • Statements end with semi-colon(;) • Preprocessor Directive • Escape characters • Sequential Flow • cout, getch(),return 0

3. Preprocessor directive main function Simple Program • #include<iostream> • #include<conio> • int main(){ • cout<<"Every age • has a language of its own\n"; • getch(); • return 0; • }

4. Simple Program • #include<iostream> • #include<conio> • void main(void){ • cout<<"Every age • has a language of its own\n"; • getch(); • }

5. Comments • We can comment something if we do not want it to be compiled • It is mostly used to define or explain something in the code • Single line comments // • Multi line comment  /*……….*/

6. Comments • //This is our First Program • #include<iostream> • #include<conio>//Preprocessor Directive • int main(){ //start of the function • cout<<"Every age has a language of its own\n"; • /*getch(); • return 0;*/ • }

7. Escape Characters • #include<iostream> • #include<conio> • int main(){ • cout<<“*\n**\n***\n*****\n"; • getch(); • return 0; • }

8. Escape Characters

9. Variables • A variable is a location in computer memory where a value can be stored • Every variable has two parts: • Variable type • Variable name (identifier) • i.e. int a; • Variables must be declared before they are used in program

10. 100 101 102 103 104 105 106 RAM int abc; abc=10; 10 abc

11. Variables • #include<iostream> • #include<conio> • int main(){ • int var1; • int var2; • var1=20; • var2=var1+10; • cout<<“var1+10 is :”; • cout<<var2<<endl; • getch(); • return 0; • }

13. Initialize five variables a,b,c,d,e.Display them on screen • #include<iostream> • #include<conio> • int main(){ • int a,b,c,d,e; • a=3; • b=4; • c=6; • d=e=9; • cout<<a<<endl<<b<<endl<<c<<“ ”<<d; • return 0; • }

14. 100 101 102 103 104 105 106 Swapping of variables 10 a int a=10; 30 b int b=30; a=b;

15. Swapping of variables • #include<iostream> • #include<conio> • int main(){ • int x,y,temp; • x=3; • y=4; • temp=x; • x=y; • y=temp; • cout<<x<<endl<<y; • return 0; • }

16. Variables Names • Following rules should follow for naming the variables: • Upper case, lower case letters and digits(0 to 9) • Underscore(_) can also be used • Name must start with a letter or underscore • Keywords cannot be used as variable name i.e. return,int, void etc.

17. Variables Names • C++ is a case sensitive language uppercase and lower case are different: a1 is different from A1 • Valid identifiers: int abc, int aBc, int first_var, int _first • Invalid identifiers: int 3bc, int a*b, int #a

18. Adding Two Integers • #include<iostream> • #include<conio> • int main(){ • int integer1, integer2, sum; • cout<<“Enter first integer\n”; • cin>>integer1; • cout<<“Enter second interger\n”; • cin>>integer2; • sum = integer1+integer2; • cout<<“Sum is :”<<sum<<endl; • getch(); • return 0; • }

23. Arithmetic Operators

24. Problem • Ask user to enter a three digit number.Then display the number in reverse order

25. #include<iostream> • #include<conio> • void main(){ • cout<<"Enter a three digit number\n"; • int a; • cin>>a; • cout<<a%10; • a=a/10; • cout<<a%10; • a=a/10; • cout<<a; • getch(); • }

27. Variables Types

28. Using Character • #include<iostream> • #include<conio> • int main(){ • char x; • x=‘a’; • cout<<x; • getch(); • return 0; • }