sri ramanuja seva

Past year exam questions and answers. Programming in C (CS 3251). Unit 1. Assignment operator and equality operator.
(See Part 4 here: 16 marks Q-A on struct (Unit 4). )

Q.3. (April/May 2022) 2 marks, Unit 1.

What is the difference between a=5 and a==5?

Answer.

• a = 5 is an assignment statement.
  • (= is assignment operator.)
  • Assigns the value 5 to the variable a.
• a == 5 is a comparison.
  • (== is equality or comparison operator.)
  • Checks whether value of a is equal to 5.
  • Returns 1 if equal, returns 0 if not equal.

Supplementary Notes

Assignment Operator (=)

• It is a binary operator.
• Assigns the value on the right hand side to the variable on the left hand side.

Example 1:

int a;
a = 10;      //assigns value 10 to a
printf("%d", a);

Output:
10

Example 2:

int a, b;
a = 20; //assigns the value 20 to a
b = a; //assigns the value of a (that is, 20) to b
printf(“%d %d”, a, b);
Output:
20 20

Example 3:

int x, y, z;
y = 20, z = 5;      //y is now 20, and z is now 5
x = y + z;          // x is now 25
printf("%d", x);

Output:

25

Example 4:

int a, b, c;
a = b = c = 25;
printf("%d %d %d", a, b, c);

Output:

25 25 25

Equality Operator (==)

• Compares two values.
• If the values are equal, returns 1.
• If the two values are not equal, returns 0.
• In C, 1 means true, and 0 means false.

Example 1:

int a = 30, b = 20;
if (a == b) //checks if a is equal to b 
{
    printf("The two values are equal.");
}
else
{
    printf("The two values are not equal.");
}

Output:

The two values are not equal.

Example 2:

int a = 10, b = 10;
if (a == b) //checking whether a is equal to b 
    printf("Equal");
else
    printf("Not equal");

Output:

Equal

Important

Do not confuse:

• = (assignment operator) with == (equality operator).
• = assigns a value.
• == compares two values.