DECISION MAKING AND BRANCHING | Operators in C Program Language | simple c programs with output

DECISION MAKING AND BRANCHING

Introduction:
             C Language must be able to perform different sets of actions depending on the circumstances. A C program is a set of statements which are normally executed sequentially n the order in which they appear. This happens when no options or no repetitions of certain calculations are necessary.
However,in practice, we have a number of situations where we may have to change the order of execution of statements based on certain conditions,repeat a group of statements until certain specified conditions are met. This involves a kind of decision making to see whether a particular condition has occurred or not and then direct the computer to execute certain
statements accordingly.

   C has 4 decision making instructions, They are:
  1. If -Else Statement
  2. Switch Statement
  3. Conditional Operator Statement
  4. Goto Statement.



The IF Statement:
                       The IF Statement is a powerful decision making statement and is used to control the flow of execution of statements.

The General form of IF statement is look like this:

             if(This condition is true)

                 execute this statement;

The keyword 'IF' tells the compiler that what follows is a decision control instruction.The condition following the keyword 'If' is always enclosed within a pair of Parenthesis.
     
        It allows the computer to evaluate the expression first and then depending on whether the value of the expression (relation or condition) is 'TRUE' (non-zero) or FALSE (zero),it transfers the control to a particular statement. This point of program has two paths to follow one for the TRUE condition and other is for FALSE condition.

       As a general rule, we express a condition using 'C' relational operators, the following table shows how they are evaluated:

Hierarchy of operators:
           Operator                       Type
 
             !                        Logical NOT     

           *,/,%                  Arithmetic and Modulus

           +, -                       Arithmetic

          <>,<=,>=                    Relational         

           ==,!=                     Relational

            &&                        Logical AND

            ||                        Logical OR

             =                        Assignment


Demonstration of "IF" statement
Example:1

                main()
  {
    int num;
    printf("Enter a number less than 10");
    scanf("%d",&num);
    if(num <= 10)
    printf(" How nice you are");
  }

Description:
     On execution of this program, if you type a number less
than or equal to 10, you get a message on the screen through
printf(). If you type some other number the program doesn't
do anything.