Operators and Expressions

Operators are the symbols which performs specific task on the operands.

Operands are the data item on which an operator acts.

There are three types of operators on the basis of operands

Unary operator → operators which performs operation on single operand.
Binary operator → operators which performs operation on two operands.
Ternary operator → operators which performs operation on three operands.

Operators on the basis of operations

Arithmetic operator
Assignment operator
Relational operator
Logical operator
Bitwise operator
Conditional operator
Increment and decrement operator
sizeof operator
comma operator

Arithmetic operator

Arithmetic operators are used for numberic calculations. They are of two types-

Unary arithmetic operator
- requires only one operand.
- Example → -y
- here '-' changes the sign of the operand y.
Binary arithmetic operator
- require two operands. There are five binary arithmetic operators.
  - + → addition
  - - → subtraction
  - * → multiplication
  - / → division
  - % → remainder
- ☆ note → (%) modulus operator cannot be applied with floating point operands.

Assignment Operator '='

A value can be stored in a variable using assignment operator.
The operand on the ldft hand side should be a variable, while the operand on the right hand side xan be any variable, constant or expression.
Examples:
a = 6;
a = x + y - 6;

Increment and Decrement Operators

There are two operators increment ( ++ ) and decrement ( -- ).
These are unary operators as they operate on single operand.
( ++ ) increments the value of the variable by 1 and ( -- ) decrements the value of the variable by 1.
++x → x = x + 1
--x → x = x - 1
These operators are of two types
1. Prefix increment / decrement → ( ++x or --x )
2. Postfix increment / decrement → ( x++ or x-- )

Prefix Increment / Decrement

The value of variable is first incremented / decrement then the new value is used in the operation

                            
#include <stdio.h>

int main()
{
    int x = 5, y, b = 10, c;
    y = ++x;
    c = --b;
    printf("The value of y is = %d and x is = %d\n", y, x); // The value of y is = 6 and x is = 6
    printf("The value of c is = %d and c is = %d\n", c, b); // The value of c is = 9 and c is = 9
    return 0;
}

Postfix Increment / Decrement

The value of variable is used in the operation and then increment / decrement is performed.

                            
#include <stdio.h>

int main()
{
    int x = 5, y, b = 10, c;
    y = x++;
    c = b--;
    printf("The value of y is = %d and x is = %d\n", y, x); // The value of y is = 5 and x is = 6
    printf("The value of c is = %d and c is = %d\n", c, b); // The value of c is = 10 and c is = 9
    return 0;
}

Relational Operators

These are used to compare values of two expressions.
If the relation is true then value of relation expression is 1 and if the relation is false then the value of expression is 0.
The relational operators are-
- < ( less than )
- ≤ ( less than or equal to )
- = = ( equal to )
- != ( Not equal to )
- > ( Greater than )
- ≥ ( Greater than or equal to )

Logical or Boolean Operators

These combines two or more expressions
For combining these expressions we use logical operators
These operators return 0 or 1.
Three logical operators
1. && ( AND )
2. || ( OR )
3. ! ( NOT )

Conditional Operator

Also known as ternary operator ( ? and : ) which requires three expressions as operands.
TestExpression ? expression1 : expression2
- If testExpression is true, then expression1 is evaluated.
- If textExpression is false, then expression2 is evaluated.

                        
a < b ? printf("a is smaller") : printf("b is smaller");

Bitwise Operators

These are used for operations on individual bits.
These operate on integers only.
Bitwise operators are
- & ( bitwise AND )
- | ( bitwise OR )
- ~ ( one's complement )
- << ( left shift )
- >> ( right shift )
- ^ ( bitwise XOR )

sizeof Operator

gives the size of a any data type

                        
sizeof(int); // 4
sizeof(float); // 4

Comma operator

used to separate variable, expressions.

                        
int a,b,c;

Precedence and Associativity of Operators

Operator precedence determines which operation is performed first in an expression with more than one operators with different precedence.
Operators Associativity is used when two operators of same precedence appear in an expression. Associativity can be either Left to Right or Right to Left.

Operator

Description

Precedence Level

Associativity

( )

[ ]

→

Function call

Array subscript

Arrow operator

Dot operator

left to right

sizeof

Unary plus

Unary minus

increment

decrement

logical NOT

one's complement

indirection

address

sizeof

left to right

multiplicaiton

division

modulus

left to right

addition

subtraction

left to right

left shift

right shift

left to right

less than

less than or equal to

greater than

greater than or equal to

left to right

= =

equal to

not equal to

left to right

Bitwise AND

left to right

Bitwise XOR

left to right

Bitwise OR

left to right

logical AND

left to right

logical OR

left to right

? :

conditional operator

right to left

*= /= %=

+= -=

&= ^= |=

<<= >>=

assignment operator

right to left

comma operator

left to right

Questions

a = 8, b = 4, c = 2, d = 1, e = 5 , f = 20
a+b-(c+d)*3%e+f/9
a =17, b = 5, c = 6, d = 3, e = 5
a % 6 - b / 2 + ( c * d - 5 ) / e
a = 4, b = 5, C = 6, d = 3, e = 5, f = 10
a*b-c/d<e+f
a = 8, b = 5, c = 8, d = 3, e = 65, f = 10, g = 2, h = 5, k = 2
a-b+c/d== e/f - g+h %k
a = 8, b = 3, C = 2, d = 3, e = 2, f = 11
a - b || ( a- b * C ) + d && e - f % 3

Control Statements

Control statement allow us to change sequence of our program. It enable us to specify the order in which the various instructions in the program are to be executed.
Control Statements define how the control is transferred to other parts of the program.
In C there are four types of control statements
1. if...else
2. goto
3. switch
4. loop
  - while
  - do...while
  - for

If...else

This statement is used to test a condition and take one of the two possible actions.
If the condition is true then a particular block of statements is executed, otherwise another block of statements is executed.

Syntax ↓

                    
if(condition)
    statement1;

                    
if(condition)
{
    statement;
    ......
    .... 
}

syntax 2↓

                    
if(condition)
    statement1;
else 
    statement2;
// Here if the condition is true then statement1 is executed and if it is false then statement2 is executed.

                    
if(condition)
{
    statement;
    ......
    .... 
}
else 
{
    statement;
    ......
    ....  
}

Nesting of if...else

Having if...else statement in the if block or the else block. This is called nesting of if...else statements.

Syntax ↓

                        
if(condition 1)
{
    if(condition 2)
        statementA1;
    else 
        statementA2;
}
else 
{
    if(condition 3)
        statementB1;
    else 
        statementB2;
}

else if Ladder

This is a type of nesting in which there is an if...else statement in every else part except the last else part. This type of nesting is frequently used in programs and is also known as else if ladder.

                        
if(condition1)
    statementA;
else 
    if(condition2)
        statementB;
    else 
        if(condition3)
            statementC;
        else 
            statementD;

Loops

Loops are used when we want to execute a block of statements several times.
There are three loop statements in C.
- while
- do while
- for

while loop

                        
while(conditon)
{
    statement;
    statement;
}

Program to print the numbers from 1 to 10 using while loop.

                            
#include<stdio.h> 
int main()
{
    int i = 1;
    while(i<=10)
    {
        printf("%d\t",i);
        i++;
    }
    printf("\n");
}

Output ↓

                            
1   2   3   4   5   6   7   8   9   10

do...while loop

The 'do...while' statement is also used for looping.

Syntax ↓

                    
do 
{
    statement;
    statement;
    .......
}while(condition);

Program to print the numbers from 1 to 10 using do...while loop

                            
#include<stdio.h> 
int main()
{
    int i = 1;
    do
    {
        printf("%d\t",i);
        i++;
    }while(i<=10);
    printf("\n");
}

Output↓

                            
1   2   3   4   5   6   7   8   9   10

for loop

The 'for' statement is very useful while programming in C.

Syntax ↓

                        
for(expression1;expression2;expression3)
{
    statement;
    statement;
}

Nesting of Loops

When a loop is written inside the body of another loop, then it is known as nesting of loops.

Program to understand nesting of for loop

                            
#include<stdio.h>
int main()
{
    int i,j;
    for(i=1;i<=3;i++) // outer loop
    {
        printf("i = %d\n",i);
        for(j=1;j<=4;j++)
            printf("j = %d\t",j);
        printf("\n");
    }
    return 0;
}

Break Statement

Break statement is used inside loops and switch statements.
Sometimes it becomes necessary to come out of the loop even before the loop condition becomes false.
In such case break statement is used to terminate the loop.
This statement causes an immediate exit from that loop in which this statement appears.
It can be written as ↓
break;
When break statement is encountered loop is terminated and the control is transferred to the statement immediately after the loop.
The break statement is generally written along with a condition.
If break is written inside a nested loop structure then it causes exit from the innermost loop.

Continue Statement

The continue statement is used when we want to go to the next interation of the loop after skipping some statements of the loop.
This continue statement can be written simply as -
continue;
It is generally used with a condition. When continue statement is encountered all the remaining statement in the current iteration are not executed and the loop continues with the next iteration.

The difference between break and continue is that when break is encountered the loop terminates and the control statement is transferred to the next statement following the loop, but when a continue statement is encountered the loop is not terminated and the control is transferred to the beginning of the loop.

Goto

this is an unconditional control statement that transfers the flow of control to another part of the program.
The goto statement can be used as ↓

                    
goto label;
    .....
    .....
label:
    statement;
    ......
    ......

Here label is any valid C identifier and it is followed by a colon.
whenever the statement goto label is encountered, the control is transferred to the statement that is immediately after the label.

Program to print whether the number is even or odd.

                        
#include<stdio.h>
int main()
{
    int n;
    printf("Enter the number : ");
    scanf("%d",&n);
    if(n%2==0)
        goto even;
    else 
        goto odd;
    even :
        printf("Number is even");
        goto end;
    odd :
        printf("Number is odd");
        goto end;
    end :
        printf("\n");
        
    return 0;
}

Switch

It is used to perform different actions based on different conditions (cases).
Switch case statements follow a selection-control mechanism and allow a value to change control of execution.
This is a multi-directional conditional control statement.
Sometimes there is a need in program to make choice among number of alternatives, for making this choice, we use switch statement.
This can be written as -

                        
switch(expression)
{
    case constant1:
        statement 
        ......
        break;
    case constant2:
        statement 
        ......
        break;
    case constant3:
        statement 
        ......
        break;
    default:
        statement 
        ......
}

Switch vs if else

Switch is better for multi way branching.
Switch is faster than if...else if provided with good number of cases.
Switch looks much cleaner when you have to read it.

Programs

Program to find factorial using for loop.

                        
#include <stdio.h>

int main()
{
    int n,fact=1;
    printf("Enter the number whose factorial you want to calculate : ");
    scanf("%d",&n);
    for (int i = 1; i <= n; i++)
    {
    fact*=i;
    }
    printf("The factorial of %d is %d\n",n,fact);
    return 0;
}

Program to find factorial using while loop.

                        
#include <stdio.h>
int main()
{
    int n,fact=1;
    printf("Enter the number whose factorial you want to calculate : ");
    scanf("%d",&n);
    int i = 1;
    while(i<=n)
    {
    fact*=i;
    i++;
    }
    printf("The factorial of %d is %d\n",n,fact);
    return 0;
}

Program for using +,-,/,*,% operator in calculator

                        
#include <stdio.h>
int main()
{
    int a, b;
    char op;
    printf("Enter the value of 'a' and 'b' : ");
    scanf("%d%d", &a, &b);
    printf("Enter the operation from : '+', '-', '/', '*', '%%' : ");
    scanf(" %c", &op);
    if (op == '+')
        printf("The sum of %d and %d is %d\n", a, b, a + b);
    else if (op == '-')
        printf("The subtraction of %d and %d is %d\n", a, b, a - b);
    else if (op == '*')
        printf("The multiplication of %d and %d is %d\n", a, b, a * b);
    else if (op == '/')
        printf("The division of %d and %d is %d\n", a, b, a / b);
    else if (op == '%')
        printf("The modulus of %d and %d is %d\n", a, b, a % b);
    else
        printf("You enter wrong operator\n");

    return 0;
}

                            
#include <stdio.h>

int main()
{
    char op;
    int a, b, c;
    printf("Enter the value of a and b : ");
    scanf("%d%d", &a, &b);
    printf("Enter the operator : ");
    scanf(" %c",&op);
    switch (op)
    {
    case '+':
        c = a + b;
        printf("sum = %d\n", c);
        break;
    case '-':
        c = a - b;
        printf("subraction = %d\n", c);
        break;
    case '*':
        c = a * b;
        printf("multiplication = %d\n", c);
        break;
    case '/':
        c = a / b;
        printf("division = %d\n", c);
        break;
    case '%':
        c = a % b;
        printf("remainder = %d\n", c);
        break;

    default:
        printf("Entered the wrong operator\n");
        break;
    }
    return 0;
}

Program to find whether the alphabet is a vowel or consonant

                            
#include <stdio.h>

int main()
{
    char ch;
    printf("Enter alphabet : ");
    scanf("%c", &ch);
    switch (ch)
    {
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
        printf("The entered alphabet is a vowel\n");
        break;
    default:
        printf("The entered alphabet is a consotant\n");
        break;
    }
    return 0;
}

Program to print
*
* *
* * *
* * * *
* * * * *

                                                   
#include <stdio.h>

int main()
{
    for (int i = 1; i <= 5; i++)
    {
        for (int j = 1; j <= i; j++)
        {
            printf("* ");
        }
        printf("\n");
    }
    return 0;
}

Program to print
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5

                            
#include 

int main()
{
    for (int i = 1; i <= 5; i++)
    {
        for (int j = 1; j <= i; j++)
        {
            printf("%d ",j);
        }
        printf("\n");
    }
    return 0;
}

Program to print
1
2 2
3 3 3
4 4 4 4
5 5 5 5 5

                            
#include <stdio.h>

int main()
{
    for (int i = 1; i <= 5; i++)
    {
        for (int j = 1; j <= i; j++)
        {
            printf("%d ",i);
        }
        printf("\n");
    }
    return 0;
}

Program to print

* * * * *
* * * *
* * *
* *
*

                            
#include <stdio.h>
int main()
{
    for(int i = 5;i>=1;i--)
    {
        for(int j=i;j>=1;j--)
        {
            printf("* ");
        }
        printf("\n");
    }
    return 0;
}

Program to print

                        
        *
      * *
    * * *
  * * * *
* * * * *

                            
#include <stdio.h>
int main()
{
    for(int i = 5;i>=1;i--)
    {
        for(int j=i;j>1;j--)
        {
            printf("_");
        }
        for(int k = 1;k<=5-i+1;k++)
        {
            printf("*");
        }
        printf("\n");
    }
    return 0;
}

Write a program to enter a number and find the reverse of that number.

                            
#include <stdio.h>

int main() {
    
    int num = 3354, rev = 0;
    while (num > 0)
    {
        rev *= 10;
        rev += (num % 10);
        num /= 10;
    }
    printf("The reverse is : %d", rev);
    
    return 0;
}