What is an Expression and Operator? Discuss Operator Associativity in C

Expression is a combination of operands (variables, constants) and operators that evaluates to a single value. Operator is a symbol that performs a specific operation on operands.

Expression

An expression in C is any valid combination of operators, constants, and variables that produces a result.

Examples:

• a + b → Arithmetic expression
• x > y → Relational expression
• a = 10 → Assignment expression

Operator

An operator is a special symbol that tells the compiler to perform a mathematical or logical operation.

Types: Arithmetic (+, -, *, /, %), Relational (<, >, ==), Logical (&&, ||, !), Assignment (=), etc.

Operator Associativity

Associativity defines the direction in which operators of the same precedence are evaluated in an expression — either Left to Right (L→R) or Right to Left (R→L).

Operator Type	Operators	Associativity
Arithmetic	*, /, % then +, -	Left to Right
Relational	<, >, <=, >=	Left to Right
Assignment	=, +=, -=	Right to Left
Unary	++, --, !	Right to Left

Example: In a = b = c = 5;, assignment is R→L, so c=5 is evaluated first, then b=c, then a=b.

Conclusion: Associativity resolves ambiguity when multiple operators of equal precedence appear in a single expression.

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Program to Find Factorial Using Recursion

Recursion is a technique where a function calls itself to solve a smaller sub-problem until a base condition is met.

Logic: factorial(n) = n × factorial(n-1), with base case factorial(0) = 1

#include <stdio.h>

int factorial(int n) {
    if (n == 0 || n == 1)
        return 1;           // Base condition
    else
        return n * factorial(n - 1);  // Recursive call
}

int main() {
    int num;
    printf("Enter a number: ");
    scanf("%d", &num);
    printf("Factorial of %d = %d", num, factorial(num));
    return 0;
}

Sample Output:

Enter a number: 5
Factorial of 5 = 120

Explanation of Recursive Calls for n=5:

• factorial(5) → 5 × factorial(4)
• factorial(4) → 4 × factorial(3)
• factorial(3) → 3 × factorial(2)
• factorial(2) → 2 × factorial(1)
• factorial(1) → returns 1 (base case)

Result: 5 × 4 × 3 × 2 × 1 = 120