C notes from scratch to advance | Conditional Instructions in C | #C

C is a programming language as we have discussed earlier about languages and Programming Languages. C is one of the oldest and finest programming languages.

In previous, we have discussed about C basics , what is C , What is Programming , What is computer language , uses and all in chapter 0. And in chapter 1 we have discussed variables, nomenclature , constants , types , keywords , basic structure of C program including Instructions and Operators and we have made our first program also.

Links of previous notes : 

Chapter 0 (basics) : click here

Chapter 1 (Variable,Constant and Keywords) :  click here 

Chapter 2 (Instructions and operators) : click here

• If it’s raining I will take umbrella.
• I will celebrate my birthday if my birthday is on Sunday.
• I will watch a movie if it’s Sunday.
• I will play Cricket if I had completed my HomeWork.
• If I will start the bike then I will meet you.

In Above all statements the work is all dependent on the conditions ( like : if this will happen then this will happen )

Explaination : the two conditions of the above

• If it’s raining I will take umbrella.
  • If it’s not raining I will not take umbrella.
• I will celebrate my birthday if my birthday is on Sunday.
  • I will not celebrate my birthday if my birthday is not on Sunday.
• I will watch a movie if it’s Sunday.
  • I will not watch a movie if it’s not Sunday.
• I will play Cricket if I had completed my HomeWork.
  • I will not play Cricket if I had not completed my HomeWork.
• If I will start the bike then I will meet you.
  • If I will not start the bike then I will not meet you.

All these are decisions that depend on conditions being met.

In ‘C’ language, too, we must be able to execute instructions on a condition(s) being met.

Decision-making instructions in C

• If-else statement
• Switch statement

If-else statement

The syntax of an if-else statement in c looks like this:

if ( condition to be checked)

{

              Statements-if-condition-true ;

}

else

{

              statements-if-condition-false ;

}

Example : 

int a=23;
if (a>18)

{
           printf(“you can drive\n”);
}

Note that else block is not necessary but optional.

Relational Operators in C

Relational operators are used to evaluate conditions (true or false) inside the if statements. Some examples of relational operators are:

Important Note: 

‘=’ is used for an assignment, whereas ‘==’ is used for an equality check.

The condition can be any valid expression. In C, a non-zero value is considered to be true.

Logical Operators 

&&, ||, and ! are the three logical operators in C. These are read as “and,””or,” and “not.” They are used to provide logic to our c programs.

Use of logical operators: 

if (condition)

{


// statements ;


}


else if (condition)

{ 

//statements;

}


else 

{ 

//statements;

}

Condition ? expression-if-true ; expression-if-false

Here, ‘?’ and ‘:’ are Ternary operators.

Switch case-control instruction

Switch-case is used when we have to make a choice between the number of alternatives for a given variable.

Syntax,

Switch(integer-expression)


{


           Case c1:


                   Code;


           Case c2: 

                   //c1,c2,c3 are constants


                   Code; 

                   //Code is any valid C code


            Case c3:


                   Code;


             default:


                    Code;


}