COMPUTER PROGRAMMING (CT 101) – Chapter 3
In C, operators and expressions are the fundamental tools for performing calculations and making logical decisions. An operator is a symbol that performs an operation on one or more operands, while an expression is a combination of these operators and operands that results in a single value. Mastering them is essential for writing effective C programs.
Chapter Information
Chapter 3: Operators and Expressions (4 hours) – 4 marks
Course: Computer Programming (CT 101), I Year I Part
Description: This guide provides a complete overview of C Operators and Expressions, covering arithmetic, logical, bitwise operators, precedence, associativity, and more, as per the IOE syllabus.
Credit: Sujan Karki
Table of Contents
Detailed Chapter Notes
3.1 Operators
Operators are symbols that perform operations on variables and values (operands). C operators can be classified by the number of operands they take:
- Unary: Takes one operand (e.g.,
-a,++a). - Binary: Takes two operands (e.g.,
a + b). - Ternary: Takes three operands (e.g., the conditional operator
? :).
3.1.1 Arithmetic Operators
Used for mathematical calculations.
| Operator | Name | Example | Description |
|---|---|---|---|
+ | Addition | a + b | Adds two operands. |
- | Subtraction | a - b | Subtracts the second operand from the first. |
* | Multiplication | a * b | Multiplies two operands. |
/ | Division | a / b | Divides the numerator by the denominator. |
% | Modulus | a % b | Returns the remainder of an integer division. |
3.1.2 Logical Operators
Used to combine or evaluate logical conditions. The result is always 1 (true) or 0 (false).
| Operator | Name | Example | Description |
|---|---|---|---|
&& | Logical AND | c1 && c2 | Returns 1 if both conditions c1 and c2 are true. |
|| | Logical OR | c1 || c2 | Returns 1 if at least one of the conditions c1 or c2 is true. |
! | Logical NOT | !c1 | Reverses the logical state; returns 1 if c1 is false, and 0 if true. |
3.1.3 Relational Operators
Used to compare two values. The result is 1 (true) or 0 (false).
| Operator | Name | Example | Description |
|---|---|---|---|
== | Equal to | a == b | Checks if the two operands are equal. |
!= | Not equal to | a != b | Checks if the two operands are not equal. |
> | Greater than | a > b | Checks if the first operand is greater than the second. |
< | Less than | a < b | Checks if the first operand is less than the second. |
>= | Greater than or equal to | a >= b | Checks if the first operand is greater than or equal to the second. |
<= | Less than or equal to | a <= b | Checks if the first operand is less than or equal to the second. |
3.1.4 Assignment Operator
Used to assign a value to a variable.
=: Assigns the value from the right side operand to the left side operand. Example:c = a + b;
3.1.5 Increment & Decrement Operators
Used to change a value by one.
| Operator | Name | Type | Description |
|---|---|---|---|
++ | Increment | ++a (Pre-fix) | Increments the value of ‘a’ before using it in the expression. |
++ | Increment | a++ (Post-fix) | Uses the current value of ‘a’ in the expression, then increments it. |
-- | Decrement | --a (Pre-fix) | Decrements the value of ‘a’ before using it in the expression. |
-- | Decrement | a-- (Post-fix) | Uses the current value of ‘a’ in the expression, then decrements it. |
3.1.6 Bitwise Operators
Used to perform operations on the binary (bit-level) representation of integer data.
| Operator | Name | Description |
|---|---|---|
& | Bitwise AND | Sets each bit to 1 if both corresponding bits are 1. |
| | Bitwise OR | Sets each bit to 1 if at least one of the corresponding bits is 1. |
^ | Bitwise XOR | Sets each bit to 1 if the corresponding bits are different. |
~ | Bitwise NOT (Complement) | Inverts all the bits of the operand. |
<< | Left Shift | Shifts bits to the left, filling trailing bits with 0s. |
>> | Right Shift | Shifts bits to the right. |
3.1.7 Special Operators
sizeofoperator: A unary operator that returns the size of a variable or data type in bytes. Example:sizeof(int)typically returns 4.- Comma operator (
,): Links multiple expressions. They are evaluated from left to right, and the value of the entire expression is the value of the rightmost expression. Example:x = (a=1, b=2, a+b);will result inxbeing assigned the value 3. - Conditional operator (
? :): The only ternary operator in C. It’s a shorthand for an if-else statement.
Syntax:condition ? value_if_true : value_if_false;
Example:max = (a > b) ? a : b;
3.2 Expressions
An expression is a combination of operators and operands that yields a single value.
3.2.1 Arithmetic Expressions & Shorthand Assignment
An arithmetic expression involves numeric values and arithmetic operators. Shorthand assignment operators provide a concise way to modify a variable.
| Shorthand | Equivalent to |
|---|---|
a += b; | a = a + b; |
a -= b; | a = a - b; |
a *= b; | a = a * b; |
a /= b; | a = a / b; |
a %= b; | a = a % b; |
3.2.2 Evaluation of Expressions
C evaluates expressions based on a set of rules. The most important rules are precedence and associativity.
3.2.3 Precedence & Associativity of Operators
- Precedence: Determines which operator is performed first in an expression with multiple operators. For example, multiplication (
*) has higher precedence than addition (+), so2 + 3 * 4is evaluated as2 + 12. - Associativity: Determines the order of evaluation for operators with the same precedence. Most operators are left-to-right associative (e.g.,
100 / 10 / 2is evaluated as(100 / 10) / 2). Assignment and unary operators are right-to-left associative.
Operator Precedence and Associativity Table
| Priority | Operator Type | Operators | Associativity |
|---|---|---|---|
| 1 (High) | Postfix | () [] -> . ++ -- | Left-to-right |
| 2 | Unary | + - ! ~ ++ -- (type) * & sizeof | Right-to-left |
| 3 | Multiplicative | * / % | Left-to-right |
| 4 | Additive | + - | Left-to-right |
| 5 | Shift | << >> | Left-to-right |
| 6 | Relational | < <= > >= | Left-to-right |
| 7 | Equality | == != | Left-to-right |
| 8 | Bitwise AND | & | Left-to-right |
| 9 | Bitwise XOR | ^ | Left-to-right |
| 10 | Bitwise OR | | | Left-to-right |
| 11 | Logical AND | && | Left-to-right |
| 12 | Logical OR | || | Left-to-right |
| 13 | Conditional | ?: | Right-to-left |
| 14 | Assignment | = += -= *= /= %= etc. | Right-to-left |
| 15 (Low) | Comma | , | Left-to-right |
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