In C language, assignment operators are used to assign values to variables. The most basic assignment operator is =, but there are also compound assignment operators that combine an arithmetic operation with assignment, making the code more concise.

Basic Assignment Operator

1. = (Simple Assignment Operator):
   • Assigns the value on the right-hand side to the variable on the left-hand side.
   • Example:

     int a;
     a = 10; // Assigns the value 10 to variable a
     

Compound Assignment Operators

Compound assignment operators combine an arithmetic or bitwise operation with an assignment. These operators are shorthand for the operation and assignment combined.

1. += (Addition Assignment):

   • Adds the right operand to the left operand and assigns the result to the left operand.
   • Equivalent to a = a + b.
   • Example:

     int a = 5;
     a += 3; // a becomes 8
     

2. -= (Subtraction Assignment):

   • Subtracts the right operand from the left operand and assigns the result to the left operand.
   • Equivalent to a = a - b.
   • Example:

     int a = 5;
     a -= 2; // a becomes 3
     

3. *= (Multiplication Assignment):

   • Multiplies the left operand by the right operand and assigns the result to the left operand.
   • Equivalent to a = a * b.
   • Example:

     int a = 5;
     a *= 2; // a becomes 10
     

4. /= (Division Assignment):

   • Divides the left operand by the right operand and assigns the result to the left operand.
   • Equivalent to a = a / b.
   • Example:

     int a = 10;
     a /= 2; // a becomes 5
     

5. %= (Modulus Assignment):

   • Computes the remainder of dividing the left operand by the right operand and assigns the result to the left operand.
   • Equivalent to a = a % b.
   • Example:

     int a = 10;
     a %= 3; // a becomes 1
     

6. &= (Bitwise AND Assignment):

   • Performs a bitwise AND operation on the left operand with the right operand and assigns the result to the left operand.
   • Equivalent to a = a & b.
   • Example:

     int a = 6;  // 0110 in binary
     a &= 3;     // 0011 in binary
                 // a becomes 2 (0010 in binary)
     

7. |= (Bitwise OR Assignment):

   • Performs a bitwise OR operation on the left operand with the right operand and assigns the result to the left operand.
   • Equivalent to a = a | b.
   • Example:

     int a = 6;  // 0110 in binary
     a |= 3;     // 0011 in binary
                 // a becomes 7 (0111 in binary)
     

8. ^= (Bitwise XOR Assignment):

   • Performs a bitwise XOR operation on the left operand with the right operand and assigns the result to the left operand.
   • Equivalent to a = a ^ b.
   • Example:

     int a = 6;  // 0110 in binary
     a ^= 3;     // 0011 in binary
                 // a becomes 5 (0101 in binary)
     

9. <<= (Left Shift Assignment):

   • Shifts the bits of the left operand to the left by the number of positions specified by the right operand and assigns the result to the left operand.
   • Equivalent to a = a << b.
   • Example:

     int a = 3;  // 0011 in binary
     a <<= 1;    // Shifts bits to the left by 1 position
                 // a becomes 6 (0110 in binary)
     

10. >>= (Right Shift Assignment):

    • Shifts the bits of the left operand to the right by the number of positions specified by the right operand and assigns the result to the left operand.
    • Equivalent to a = a >> b.
    • Example:

      int a = 8;  // 1000 in binary
      a >>= 2;    // Shifts bits to the right by 2 positions
                  // a becomes 2 (0010 in binary)
      

Example Program

#include <stdio.h>

int main() {
    int a = 10;

    a += 5;  // a becomes 15
    printf("a += 5: %d\n", a);

    a -= 3;  // a becomes 12
    printf("a -= 3: %d\n", a);

    a *= 2;  // a becomes 24
    printf("a *= 2: %d\n", a);

    a /= 4;  // a becomes 6
    printf("a /= 4: %d\n", a);

    a %= 5;  // a becomes 1
    printf("a %%= 5: %d\n", a);

    return 0;
}

Summary of Assignment Operators:

• =: Assigns a value to a variable.
• +=: Adds and assigns the result.
• -=: Subtracts and assigns the result.
• *=: Multiplies and assigns the result.
• /=: Divides and assigns the result.
• %=: Takes modulus and assigns the result.
• &=: Bitwise AND and assigns the result.
• |=: Bitwise OR and assigns the result.
• ^=: Bitwise XOR and assigns the result.
• <<=: Left shifts and assigns the result.
• >>=: Right shifts and assigns the result.

Assignment operators help make code concise and easier to read by combining operations with assignment in a single step, saving time and reducing redundancy.