Lecture 5

1. Lecture 5 Sept 11, 2002

2. Operators & its types • An operator is a symbol or a special character that tells the computer to perform certain mathematical or logical operations which is applied to operands to give a result. • Operators are used in programs to manipulate data and variables • Data and variables are called operands.

3. Types of Operators • Assignment operators • Arithmetic operators • Increment and decrement operators • Logical operators • Relational operators • Equality operators • Conditional operators • sizeof operator • Bitwise operators ( not im p ) Self study • Special operators ( not imp ) Self study

4. Arithmetic operators • + (Addition) • - (subtraction) • * (Multiplication) • / (Division) • % ( Modulo operation)

5. Modulus operator • This is used to find the remainder of an integer division • eg 1. 9%4 is 1 2. 3%5 is 3 3. 9%3 is 0 • The modulus operator can be used only with integers.

6. Rules in arithmeticoperations Rule # 1 • Declaration of a real data value as an integer results in truncation of fractional part to yield an integer • Problem 4: • #include<iostream.h> void main() { int a; a=3.5; cout<<a<<endl; } Output: 3

7. Rule # 2 • An arithmetic operation between integer and integer yields always an integer. • Pb 5: #include<iostream.h> void main() { int a, b, c; a=6; b=3; c=b/a; cout<<c<<endl; } output: 2

8. Rule # 3 • An arithmetic operation between real and real yields always a real result. • Problem 6: #include<iostream.h> void main() { float a=3.5, b=2.2, c; c=a/b; cout<<c<<endl; } output: 1.590

9. Rule # 4 • Operation between an integer and real always yields a real result. • Problem 7 int a=3; float b=2.2, c; c=a* b; cout<<c<<endl; output: 6.6

10. Rule # 5 • The modulus operator can be used only with integers. • Problem 8: • int a,b,c; a=9; b=4; c=a%b; cout<<c<<endl; output: 1

11. Type casting • Sometimes we are needed to force the compiler to explicitly convert the value of an expression to a particular data type. • Problem 9 • void main() { float a; int x=6, y=4; a= (float ) x/y; // type casting is done here cout<<a<<endl; } output : 1.5

12. Priority of arithmetic operators • Evaluate expression i=2* b* y/ (d+1) - x / (3 * (z + y)) ? How would you do it? What would be the result?

13. Priority Rules • BODMAS – Brackets of division, multiplication and addition, subtraction • If there are more than one set of brackets, the operations within the innermost brackets will be performed first • Incase of a tie between operations of same priority preference is given to operator which occurs first

14. Evaluation process int b=2, d=1, x=4, y=5, z=4; i=2* b* y/ (d+1) - x / (3 * (z + y)) ? i=2* 2* 5/ (1+1) – 4/ (3 * (4 + 5)) ? i=2* 2* 5/ 2 - 4/ (3 * 9 ) i=2* 2* 5/ 2 - 4/ 27 i= 4 * 5/ 2 - 4/ 27 i= 20 / 2 - 4/ 27 i= 10 -4/ 27 i= 10 - 0.148 i= 9.852

15. Assignment operators • Assignment operators are used to assign the result of an expression to a variable. • float a; // variable declaration a = 25.2; // ‘ = ‘ is assignment operator Short hand form: x=x+1; or x += 1; y=y-1; or y -= 1; z=z*(x+y); or z *=(x+y); y=y/(x+y); or y /=(x+y); x = x % z or x %=z;

16. Increment and decrement operators • ++ is increment operator. • -- decrement operator. Modes • ++a and -- a are in pre-increment mode. • a++ and a– are in post increment mode.

17. Usage • b= ++a ; or a=a+1; b=a; • b= a++; or b=a; a=a+1;

18. Problem 10 • To understand increment and decrement operators #include<iostream.h> // preprocessor directive void main() // function main { int a=10,b,c=10,d; b=++a; // eqt : a=a+1; b=a; (pre-increment) cout<<“b is “<<b<<endl; d=c++; // eqt : d=c; c=c+1; (post-increment) cout<<“d is “<<d<<endl; } Output: b is 11 d is 10

19. Relational operators • < less than • > greater than • <= less than or equal to • >= greater than or equal to • You would understand this when you are taught Control structures. Just know these operators for now.

20. Logical operators • && Logical AND • | Logical OR • ! Logical NOT • You would understand this when you are taught Control structures. Just know these operators for now.

21. Equality operators • == equal to • != not equal to • You would understand this when you are taught Control structures. Just know these operators for now.

22. Conditional operators • expr1 ? Expr2 : expr3 • You would understand this when you are taught Control structures. Just know these operators for now.

23. Problem Solving • Step 1 : Thorough understanding of the problem. • Step 2 : Frame an algorithm. • Step 3 : Develop a pseudo code. • Step 4 : Draw a flow chart. • Step 5 : Code the program.

24. Algorithm : A procedure for solving a problem in terms of : • The actions to be executed, • the order in which these actions are to be executed

25. Pseudocode : Its an informal code. • Similar to everyday english • They help programmers think out a program • Pseudocodes are then converted to the executable language statements.

26. Flow chart – It is a pictorial representation of the flow of the logic of the program. • Logic means the approach of the problem.

27. 5 lectures in a nutshell • Lec 1 : Introduction to computers • Lec 2 : Simple c++ programs ( 2 problems) • Lec 3 : Variables and Data types • Lec 4 : Repeated Variables and data types • Lec 5 : Operators, its types, and Problem Solving (8 problems ) “ This forms the basis, the core of problem solving using a higher level languages starts here “