C Operators and Expressions

01Why Do We Need Operators?

Think About Math in Real Life...

When you do math on paper, you use symbols like +, -, ×, ÷. In programming, we need the same ability - plus many more operations like comparisons (is 5 greater than 3?) and logical decisions (is this AND that true?).

Operators are the symbols that let us perform these operations in C.

Operators are symbols that tell the compiler to perform specific operations on values or variables. The values they work on are called operands.

Expression: 10 + 20

Operand

Operator

Operand

Result

Types Based on Number of Operands

Unary (1 operand)

++a, --b, !flag

Binary (2 operands)

a + b, x * y

Ternary (3 operands)

a ? b : c

02Arithmetic Operators

Used for mathematical calculations like addition, subtraction, multiplication, and division.

Key Points for Beginners

• Division (/) with integers: Result is always an integer (truncated). 10 / 3 = 3, not 3.33
• Modulus (%): Returns the remainder after division. 10 % 3 = 1 because 10 = 3×3 + 1
• ++a vs a++: ++a increments before using the value; a++ uses the value then increments

Operator	Name	Example	Result
+	Addition	10 + 3	13
-	Subtraction	10 - 3	7
*	Multiplication	10 * 3	30
/	Division	10 / 3	3 (integer)
%	Modulus (remainder)	10 % 3	1
++	Increment	a++ or ++a	a + 1
--	Decrement	a-- or --a	a - 1

▶ Try it: Demonstrates all arithmetic operators with two numbers and shows the difference between pre/post increment.

arithmetic_ops.c

1#include <stdio.h>
2
3int main() {
4    int a = 17, b = 5;
5    
6    printf("a = %d, b = %d\n\n", a, b);
7    printf("a + b = %d\n", a + b);   // 22
8    printf("a - b = %d\n", a - b);   // 12
9    printf("a * b = %d\n", a * b);   // 85
10    printf("a / b = %d\n", a / b);   // 3 (integer division)
11    printf("a %% b = %d\n", a % b);  // 2 (remainder)
12    
13    // Pre vs Post increment
14    int x = 5;
15    printf("\nx = %d\n", x);
16    printf("x++ = %d\n", x++);  // Prints 5, then x becomes 6
17    printf("Now x = %d\n", x);  // x is now 6
18    printf("++x = %d\n", ++x);  // x becomes 7, then prints 7
19    
20    return 0;
21}

Output

a = 17, b = 5

a + b = 22

a - b = 12

a * b = 85

a / b = 3

a % b = 2

x = 5

x++ = 5

Now x = 6

++x = 7

Pre vs Post Increment

++x (prefix): Increment first, then use the value
x++ (postfix): Use the value first, then increment

03Relational Operators

Used to compare two values. Returns 1 (true) or 0 (false).

Operator	Meaning	Example (a=10, b=5)	Result
==	Equal to	a == b	0 (false)
!=	Not equal to	a != b	1 (true)
>	Greater than	a > b	1 (true)
<	Less than	a < b	0 (false)
>=	Greater or equal	a >= b	1 (true)
<=	Less or equal	a <= b	0 (false)

▶ Try it: Compares two numbers and prints 1 for true, 0 for false.

relational_ops.c

1#include <stdio.h>
2
3int main() {
4    int a = 10, b = 5;
5    
6    printf("a = %d, b = %d\n\n", a, b);
7    printf("a == b: %d\n", a == b);  // 0 (false)
8    printf("a != b: %d\n", a != b);  // 1 (true)
9    printf("a > b:  %d\n", a > b);   // 1 (true)
10    printf("a < b:  %d\n", a < b);   // 0 (false)
11    printf("a >= b: %d\n", a >= b);  // 1 (true)
12    printf("a <= b: %d\n", a <= b);  // 0 (false)
13    
14    return 0;
15}

04Logical Operators

Used to combine or negate conditions. Essential for complex if statements.

Operator	Name	Description	Example
&&	AND	True if both are true	1 && 1 = 1, 1 && 0 = 0
\|\|	OR	True if any is true	1 \|\| 0 = 1, 0 \|\| 0 = 0
!	NOT	Reverses the value	!1 = 0, !0 = 1

▶ Try it: Shows how logical operators combine conditions and how NOT reverses boolean values.

logical_ops.c

1#include <stdio.h>
2
3int main() {
4    int a = 1, b = 0;  // 1 = true, 0 = false
5    
6    printf("a = %d (true), b = %d (false)\n\n", a, b);
7    
8    // AND: both must be true
9    printf("a && b = %d\n", a && b);  // 0 (false)
10    printf("a && a = %d\n", a && a);  // 1 (true)
11    
12    // OR: at least one must be true
13    printf("a || b = %d\n", a || b);  // 1 (true)
14    printf("b || b = %d\n", b || b);  // 0 (false)
15    
16    // NOT: reverse the value
17    printf("!a = %d\n", !a);  // 0 (false)
18    printf("!b = %d\n", !b);  // 1 (true)
19    
20    // Practical example
21    int age = 25;
22    int hasLicense = 1;
23    if (age >= 18 && hasLicense) {
24        printf("\nYou can drive!\n");
25    }
26    
27    return 0;
28}

05Bitwise Operators

Operate on individual bits of integers. Used in low-level programming, flags, and optimization.

Op	Name	Description
&	AND	1 if both bits are 1
\|	OR	1 if any bit is 1
^	XOR	1 if bits are different
~	NOT	Flip all bits
<<	Left Shift	Multiply by 2ⁿ
>>	Right Shift	Divide by 2ⁿ

Visual: 5 & 3 (Bitwise AND)

5 =0101

3 =0011

5 & 3 =0001= 1

▶ Try it: Demonstrates bitwise operations and shows how left/right shift multiplies or divides by powers of 2.

bitwise_ops.c

1#include <stdio.h>
2
3int main() {
4    int a = 5, b = 3;  // 5 = 0101, 3 = 0011
5    
6    printf("a = %d (0101), b = %d (0011)\n\n", a, b);
7    
8    printf("a & b  = %d\n", a & b);   // 1 (0001)
9    printf("a | b  = %d\n", a | b);   // 7 (0111)
10    printf("a ^ b  = %d\n", a ^ b);   // 6 (0110)
11    printf("~a     = %d\n", ~a);      // -6 (inverts all bits)
12    
13    // Shift operators
14    printf("\na << 1 = %d\n", a << 1);  // 10 (multiply by 2)
15    printf("a << 2 = %d\n", a << 2);    // 20 (multiply by 4)
16    printf("a >> 1 = %d\n", a >> 1);    // 2 (divide by 2)
17    
18    return 0;
19}

Shift Trick

x << n = x × 2ⁿ (fast multiplication)
x >> n = x ÷ 2ⁿ (fast division)

06Assignment Operators

Used to assign values to variables. Compound operators combine assignment with another operation.

Operator	Equivalent
a = b	a = b
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

Operator	Equivalent
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

▶ Try it: Shows compound assignment operators in action — they modify the variable in place.

assignment_ops.c

1#include <stdio.h>
2
3int main() {
4    int x = 10;
5    printf("Initial x = %d\n\n", x);
6    
7    x += 5;   printf("x += 5  → x = %d\n", x);  // 15
8    x -= 3;   printf("x -= 3  → x = %d\n", x);  // 12
9    x *= 2;   printf("x *= 2  → x = %d\n", x);  // 24
10    x /= 4;   printf("x /= 4  → x = %d\n", x);  // 6
11    x %= 4;   printf("x %%= 4  → x = %d\n", x); // 2
12    
13    return 0;
14}

07Other Operators

sizeof Operator - Getting Size in Bytes

sizeof is a compile-time operator that returns the size (in bytes) of a variable or data type. It's not a function - no function call overhead!

size_t sizeof(type_or_variable)

Returns: Size in bytes (type: size_t, use %zu to print)

Usage: sizeof(int), sizeof(arr), sizeof(x)

Operator	Description	Example
sizeof()	Returns size in bytes (compile-time)	sizeof(int) → 4
? :	Ternary (shorthand if-else)	a > b ? a : b
&	Address-of operator	&x → 0x7fff...
*	Dereference (get value at address)	*ptr → value
(type)	Type cast (convert to type)	(float)5 → 5.0
,	Comma (evaluates left-to-right)	(a=1, b=2) → 2

▶ Try it: Demonstrates sizeof, ternary operator, address-of, and type casting.

other_ops.c

1#include <stdio.h>
2
3int main() {
4    // sizeof - get size in bytes
5    printf("sizeof(int): %zu bytes\n", sizeof(int));
6    printf("sizeof(char): %zu byte\n", sizeof(char));
7    
8    // Ternary operator (condition ? if_true : if_false)
9    int a = 10, b = 20;
10    int max = (a > b) ? a : b;
11    printf("\nMax of %d and %d is %d\n", a, b, max);
12    
13    // Address-of operator
14    int x = 42;
15    printf("\nValue of x: %d\n", x);
16    printf("Address of x: %p\n", (void*)&x);
17    
18    // Type casting
19    int num = 7;
20    printf("\n7 / 2 = %d (int)\n", num / 2);
21    printf("7 / 2 = %.2f (float)\n", (float)num / 2);
22    
23    return 0;
24}

08C Expressions

An expression is a combination of operands (values/variables) and operators that evaluates to a single value. Expressions are the building blocks of C statements.

Expression Type	Description	Example
Constant	Contains only constant values	5 + 3 * 2
Integral	Produces integer result	a + b * c
Floating	Produces float/double result	3.14 * r * r
Relational	Produces true (1) or false (0)	a > b
Logical	Combines conditions	a > 0 && b > 0
Pointer	Produces memory address	&x, ptr + 1

▶ Try it: Demonstrates different types of expressions and how they evaluate to single values.

expressions.c

1#include <stdio.h>
2
3int main() {
4    int a = 10, b = 5;
5    float pi = 3.14, r = 2.0;
6    
7    // Constant expression (evaluated at compile time)
8    int size = 5 + 3 * 2;  // 11
9    printf("Constant: 5 + 3 * 2 = %d\n", size);
10    
11    // Arithmetic expression
12    int sum = a + b * 2;   // 10 + 10 = 20
13    printf("Arithmetic: a + b * 2 = %d\n", sum);
14    
15    // Floating expression
16    float area = pi * r * r;  // 3.14 * 4 = 12.56
17    printf("Floating: pi * r * r = %.2f\n", area);
18    
19    // Relational expression (returns 0 or 1)
20    int isGreater = a > b;  // 1 (true)
21    printf("Relational: a > b = %d\n", isGreater);
22    
23    // Logical expression
24    int bothPositive = (a > 0) && (b > 0);  // 1 (true)
25    printf("Logical: (a > 0) && (b > 0) = %d\n", bothPositive);
26    
27    // Assignment expression (returns assigned value)
28    int x, y;
29    x = (y = 5) + 3;  // y=5, x=8
30    printf("Assignment: x = (y = 5) + 3 → x=%d, y=%d\n", x, y);
31    
32    // Comma expression (evaluates left-to-right, returns last)
33    int result = (a = 1, b = 2, a + b);  // result = 3
34    printf("Comma: (a=1, b=2, a+b) = %d\n", result);
35    
36    return 0;
37}

Output

Constant: 5 + 3 * 2 = 11

Arithmetic: a + b * 2 = 20

Floating: pi * r * r = 12.56

Relational: a > b = 1

Logical: (a > 0) && (b > 0) = 1

Assignment: x = (y = 5) + 3 → x=8, y=5

Comma: (a=1, b=2, a+b) = 3

Expression vs Statement

Expression: a + b — Produces a value
Statement: x = a + b; — Performs an action (ends with ;)

09Operator Precedence

When an expression has multiple operators, precedence determines which operator is evaluated first. This is why 10 + 20 * 30 equals 610, not 900!

Quick Example

10+20 * 30

* is evaluated before + (higher precedence)

= 10 + 600 = 610

Full Tutorial Available

Learn the complete precedence table, associativity rules, and the PUMAS REBL TAC memory trick.

Learn Precedence→

!Code Pitfalls: Common Mistakes & What to Watch For

These are the most common mistakes that trip up beginners. Study them carefully to avoid hours of debugging!

Using = instead of ==

main.c

if (a = 5) { }   // WRONG! This assigns 5 to a
if (a == 5) { }  // Correct! This compares a to 5

Integer Division Confusion

main.c

int result = 5 / 2;           // Result: 2, not 2.5!
float result = 5.0 / 2;        // Result: 2.5
float result = (float)5 / 2;   // Result: 2.5

Confusing & with &&

main.c

if (a & b) { }   // Bitwise AND (rarely intended)
if (a && b) { }  // Logical AND (usually intended)

11Try It Yourself

Here's a simple calculator that demonstrates arithmetic operators:

simple_calculator.c

1#include <stdio.h>
2
3int main() {
4    int a = 15, b = 4;
5    
6    // Arithmetic operators in action
7    printf("a = %d, b = %d\n\n", a, b);
8    printf("Addition:       a + b = %d\n", a + b);
9    printf("Subtraction:    a - b = %d\n", a - b);
10    printf("Multiplication: a * b = %d\n", a * b);
11    printf("Division:       a / b = %d\n", a / b);
12    printf("Modulus:        a %% b = %d\n", a % b);
13    
14    return 0;
15}

Expected Output:

a = 15, b = 4

Addition: a + b = 19
Subtraction: a - b = 11
Multiplication: a * b = 60
Division: a / b = 3
Modulus: a % b = 3

12Step-by-Step Precedence Solving

Understanding operator precedence is crucial for writing correct C code. Let's solve some complex expressions step-by-step.

Example 1: Arithmetic Precedence

result = 10 + 20 * 30 / 5 - 15

First, * and / (left to right): 20 * 30 = 600

10 + 600 / 5 - 15

Continue with /: 600 / 5 = 120

10 + 120 - 15

Now + (left to right): 10 + 120 = 130

130 - 15

Finally -: 130 - 15 = 115

result = 115

Example 2: Mixed Operators

result = 5 + 3 * 2 > 10 && 8 / 4 == 2

Arithmetic first (*, /): 3 * 2 = 6, 8 / 4 = 2

5 + 6 > 10 && 2 == 2

Then + : 5 + 6 = 11

11 > 10 && 2 == 2

Relational (>, ==): 11 > 10 = 1 (true), 2 == 2 = 1 (true)

1 && 1

Finally &&: 1 && 1 = 1 (true)

result = 1

Example 3: Assignment with Operations

int a = 5, b = 3;
result = a++ + ++b * 2

++b (pre-increment): b becomes 4, use 4

a++ + 4 * 2

Multiplication: 4 * 2 = 8

a++ + 8

a++ (post-increment): use 5, then a becomes 6

5 + 8

Addition: 5 + 8 = 13

result = 13, a = 6, b = 4

Precedence Quick Reference (High to Low)

Priority	Operators	Description
1 (Highest)	() [] -> .	Parentheses, array, member access
2	++ -- ! ~ sizeof	Unary operators (right to left)
3	* / %	Multiplication, division, modulus
4	+ -	Addition, subtraction
5	< <= > >=	Relational comparison
6	== !=	Equality comparison
7	&&	Logical AND
8	\|\|	Logical OR
9 (Lowest)	= += -= *= /=	Assignment (right to left)

When in doubt, use parentheses () to make your intention clear!

14Frequently Asked Questions

Q:What's the difference between = and ==?

= is the assignment operator — it puts a value into a variable: x = 5;

== is the equality operator — it compares two values and returns 1 (true) or 0 (false): if (x == 5)

Using = instead of == in conditions is one of the most common bugs in C!

Q:Why does 5 / 2 give 2 instead of 2.5?

When both operands are integers, C performs integer division, which truncates (cuts off) the decimal part.

To get 2.5, make at least one operand a float/double:

• 5.0 / 2 → 2.5
• 5 / 2.0 → 2.5
• (double)5 / 2 → 2.5

Q:When should I use && vs & (and || vs |)?

&& and || are logical operators — use them for conditions (if statements, loops).

& and | are bitwise operators — they work on individual bits of integers.

99% of the time, you want the double versions (&&, ||) for logic!

Q:What's the modulus operator (%) used for?

The modulus operator returns the remainder after division. Common uses:

• Check if even/odd: if (n % 2 == 0) → even
• Wrap around: index % arraySize → keeps index in bounds
• Extract digits: n % 10 → last digit
• Divisibility: if (n % 5 == 0) → divisible by 5

Q:What does the ternary operator ?: do?

It's a shorthand for if-else that returns a value:

condition ? value_if_true : value_if_false

Example: int max = (a > b) ? a : b;
This means: "If a > b, max is a; otherwise, max is b."

14Summary

What You Learned:

✓WHY: Operators let us perform math, compare values, and make decisions
✓Arithmetic: +, -, *, /, %, ++, --
✓Relational: ==, !=, >, <, >=, <=
✓Logical: &&, ||, !
✓Assignment: =, +=, -=, *=, /=, etc.
✓Precedence: *, / before +, - before comparisons before &&, ||

01Why Do We Need Operators?

Think About Math in Real Life...

Operators are the symbols that let us perform these operations in C.

Operators are symbols that tell the compiler to perform specific operations on values or variables. The values they work on are called operands.

Expression: 10 + 20

Operand

Operator

Operand

Result

Types Based on Number of Operands

Unary (1 operand)

++a, --b, !flag

Binary (2 operands)

a + b, x * y

Ternary (3 operands)

a ? b : c

02Arithmetic Operators

Used for mathematical calculations like addition, subtraction, multiplication, and division.

Key Points for Beginners

• Division (/) with integers: Result is always an integer (truncated). 10 / 3 = 3, not 3.33
• Modulus (%): Returns the remainder after division. 10 % 3 = 1 because 10 = 3×3 + 1
• ++a vs a++: ++a increments before using the value; a++ uses the value then increments

Operator	Name	Example	Result
+	Addition	10 + 3	13
-	Subtraction	10 - 3	7
*	Multiplication	10 * 3	30
/	Division	10 / 3	3 (integer)
%	Modulus (remainder)	10 % 3	1
++	Increment	a++ or ++a	a + 1
--	Decrement	a-- or --a	a - 1

▶ Try it: Demonstrates all arithmetic operators with two numbers and shows the difference between pre/post increment.

arithmetic_ops.c

1#include <stdio.h>
2
3int main() {
4    int a = 17, b = 5;
5    
6    printf("a = %d, b = %d\n\n", a, b);
7    printf("a + b = %d\n", a + b);   // 22
8    printf("a - b = %d\n", a - b);   // 12
9    printf("a * b = %d\n", a * b);   // 85
10    printf("a / b = %d\n", a / b);   // 3 (integer division)
11    printf("a %% b = %d\n", a % b);  // 2 (remainder)
12    
13    // Pre vs Post increment
14    int x = 5;
15    printf("\nx = %d\n", x);
16    printf("x++ = %d\n", x++);  // Prints 5, then x becomes 6
17    printf("Now x = %d\n", x);  // x is now 6
18    printf("++x = %d\n", ++x);  // x becomes 7, then prints 7
19    
20    return 0;
21}

Output

a = 17, b = 5

a + b = 22

a - b = 12

a * b = 85

a / b = 3

a % b = 2

x = 5

x++ = 5

Now x = 6

++x = 7

Pre vs Post Increment

++x (prefix): Increment first, then use the value
x++ (postfix): Use the value first, then increment

03Relational Operators

Used to compare two values. Returns 1 (true) or 0 (false).

Operator	Meaning	Example (a=10, b=5)	Result
==	Equal to	a == b	0 (false)
!=	Not equal to	a != b	1 (true)
>	Greater than	a > b	1 (true)
<	Less than	a < b	0 (false)
>=	Greater or equal	a >= b	1 (true)
<=	Less or equal	a <= b	0 (false)

▶ Try it: Compares two numbers and prints 1 for true, 0 for false.

relational_ops.c

1#include <stdio.h>
2
3int main() {
4    int a = 10, b = 5;
5    
6    printf("a = %d, b = %d\n\n", a, b);
7    printf("a == b: %d\n", a == b);  // 0 (false)
8    printf("a != b: %d\n", a != b);  // 1 (true)
9    printf("a > b:  %d\n", a > b);   // 1 (true)
10    printf("a < b:  %d\n", a < b);   // 0 (false)
11    printf("a >= b: %d\n", a >= b);  // 1 (true)
12    printf("a <= b: %d\n", a <= b);  // 0 (false)
13    
14    return 0;
15}

04Logical Operators

Used to combine or negate conditions. Essential for complex if statements.

Operator	Name	Description	Example
&&	AND	True if both are true	1 && 1 = 1, 1 && 0 = 0
\|\|	OR	True if any is true	1 \|\| 0 = 1, 0 \|\| 0 = 0
!	NOT	Reverses the value	!1 = 0, !0 = 1

▶ Try it: Shows how logical operators combine conditions and how NOT reverses boolean values.

logical_ops.c

1#include <stdio.h>
2
3int main() {
4    int a = 1, b = 0;  // 1 = true, 0 = false
5    
6    printf("a = %d (true), b = %d (false)\n\n", a, b);
7    
8    // AND: both must be true
9    printf("a && b = %d\n", a && b);  // 0 (false)
10    printf("a && a = %d\n", a && a);  // 1 (true)
11    
12    // OR: at least one must be true
13    printf("a || b = %d\n", a || b);  // 1 (true)
14    printf("b || b = %d\n", b || b);  // 0 (false)
15    
16    // NOT: reverse the value
17    printf("!a = %d\n", !a);  // 0 (false)
18    printf("!b = %d\n", !b);  // 1 (true)
19    
20    // Practical example
21    int age = 25;
22    int hasLicense = 1;
23    if (age >= 18 && hasLicense) {
24        printf("\nYou can drive!\n");
25    }
26    
27    return 0;
28}

05Bitwise Operators

Operate on individual bits of integers. Used in low-level programming, flags, and optimization.

Op	Name	Description
&	AND	1 if both bits are 1
\|	OR	1 if any bit is 1
^	XOR	1 if bits are different
~	NOT	Flip all bits
<<	Left Shift	Multiply by 2ⁿ
>>	Right Shift	Divide by 2ⁿ

Visual: 5 & 3 (Bitwise AND)

5 =0101

3 =0011

5 & 3 =0001= 1

▶ Try it: Demonstrates bitwise operations and shows how left/right shift multiplies or divides by powers of 2.

bitwise_ops.c

1#include <stdio.h>
2
3int main() {
4    int a = 5, b = 3;  // 5 = 0101, 3 = 0011
5    
6    printf("a = %d (0101), b = %d (0011)\n\n", a, b);
7    
8    printf("a & b  = %d\n", a & b);   // 1 (0001)
9    printf("a | b  = %d\n", a | b);   // 7 (0111)
10    printf("a ^ b  = %d\n", a ^ b);   // 6 (0110)
11    printf("~a     = %d\n", ~a);      // -6 (inverts all bits)
12    
13    // Shift operators
14    printf("\na << 1 = %d\n", a << 1);  // 10 (multiply by 2)
15    printf("a << 2 = %d\n", a << 2);    // 20 (multiply by 4)
16    printf("a >> 1 = %d\n", a >> 1);    // 2 (divide by 2)
17    
18    return 0;
19}

Shift Trick

x << n = x × 2ⁿ (fast multiplication)
x >> n = x ÷ 2ⁿ (fast division)

06Assignment Operators

Used to assign values to variables. Compound operators combine assignment with another operation.

Operator	Equivalent
a = b	a = b
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

Operator	Equivalent
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

▶ Try it: Shows compound assignment operators in action — they modify the variable in place.

assignment_ops.c

1#include <stdio.h>
2
3int main() {
4    int x = 10;
5    printf("Initial x = %d\n\n", x);
6    
7    x += 5;   printf("x += 5  → x = %d\n", x);  // 15
8    x -= 3;   printf("x -= 3  → x = %d\n", x);  // 12
9    x *= 2;   printf("x *= 2  → x = %d\n", x);  // 24
10    x /= 4;   printf("x /= 4  → x = %d\n", x);  // 6
11    x %= 4;   printf("x %%= 4  → x = %d\n", x); // 2
12    
13    return 0;
14}

07Other Operators

sizeof Operator - Getting Size in Bytes

sizeof is a compile-time operator that returns the size (in bytes) of a variable or data type. It's not a function - no function call overhead!

size_t sizeof(type_or_variable)

Returns: Size in bytes (type: size_t, use %zu to print)

Usage: sizeof(int), sizeof(arr), sizeof(x)

Operator	Description	Example
sizeof()	Returns size in bytes (compile-time)	sizeof(int) → 4
? :	Ternary (shorthand if-else)	a > b ? a : b
&	Address-of operator	&x → 0x7fff...
*	Dereference (get value at address)	*ptr → value
(type)	Type cast (convert to type)	(float)5 → 5.0
,	Comma (evaluates left-to-right)	(a=1, b=2) → 2

▶ Try it: Demonstrates sizeof, ternary operator, address-of, and type casting.

other_ops.c

1#include <stdio.h>
2
3int main() {
4    // sizeof - get size in bytes
5    printf("sizeof(int): %zu bytes\n", sizeof(int));
6    printf("sizeof(char): %zu byte\n", sizeof(char));
7    
8    // Ternary operator (condition ? if_true : if_false)
9    int a = 10, b = 20;
10    int max = (a > b) ? a : b;
11    printf("\nMax of %d and %d is %d\n", a, b, max);
12    
13    // Address-of operator
14    int x = 42;
15    printf("\nValue of x: %d\n", x);
16    printf("Address of x: %p\n", (void*)&x);
17    
18    // Type casting
19    int num = 7;
20    printf("\n7 / 2 = %d (int)\n", num / 2);
21    printf("7 / 2 = %.2f (float)\n", (float)num / 2);
22    
23    return 0;
24}

08C Expressions

An expression is a combination of operands (values/variables) and operators that evaluates to a single value. Expressions are the building blocks of C statements.

Expression Type	Description	Example
Constant	Contains only constant values	5 + 3 * 2
Integral	Produces integer result	a + b * c
Floating	Produces float/double result	3.14 * r * r
Relational	Produces true (1) or false (0)	a > b
Logical	Combines conditions	a > 0 && b > 0
Pointer	Produces memory address	&x, ptr + 1

▶ Try it: Demonstrates different types of expressions and how they evaluate to single values.

expressions.c

1#include <stdio.h>
2
3int main() {
4    int a = 10, b = 5;
5    float pi = 3.14, r = 2.0;
6    
7    // Constant expression (evaluated at compile time)
8    int size = 5 + 3 * 2;  // 11
9    printf("Constant: 5 + 3 * 2 = %d\n", size);
10    
11    // Arithmetic expression
12    int sum = a + b * 2;   // 10 + 10 = 20
13    printf("Arithmetic: a + b * 2 = %d\n", sum);
14    
15    // Floating expression
16    float area = pi * r * r;  // 3.14 * 4 = 12.56
17    printf("Floating: pi * r * r = %.2f\n", area);
18    
19    // Relational expression (returns 0 or 1)
20    int isGreater = a > b;  // 1 (true)
21    printf("Relational: a > b = %d\n", isGreater);
22    
23    // Logical expression
24    int bothPositive = (a > 0) && (b > 0);  // 1 (true)
25    printf("Logical: (a > 0) && (b > 0) = %d\n", bothPositive);
26    
27    // Assignment expression (returns assigned value)
28    int x, y;
29    x = (y = 5) + 3;  // y=5, x=8
30    printf("Assignment: x = (y = 5) + 3 → x=%d, y=%d\n", x, y);
31    
32    // Comma expression (evaluates left-to-right, returns last)
33    int result = (a = 1, b = 2, a + b);  // result = 3
34    printf("Comma: (a=1, b=2, a+b) = %d\n", result);
35    
36    return 0;
37}

Output

Constant: 5 + 3 * 2 = 11

Arithmetic: a + b * 2 = 20

Floating: pi * r * r = 12.56

Relational: a > b = 1

Logical: (a > 0) && (b > 0) = 1

Assignment: x = (y = 5) + 3 → x=8, y=5

Comma: (a=1, b=2, a+b) = 3

Expression vs Statement

Expression: a + b — Produces a value
Statement: x = a + b; — Performs an action (ends with ;)

09Operator Precedence

When an expression has multiple operators, precedence determines which operator is evaluated first. This is why 10 + 20 * 30 equals 610, not 900!

Quick Example

10+20 * 30

* is evaluated before + (higher precedence)

= 10 + 600 = 610

Full Tutorial Available

Learn the complete precedence table, associativity rules, and the PUMAS REBL TAC memory trick.

Learn Precedence→

!Code Pitfalls: Common Mistakes & What to Watch For

These are the most common mistakes that trip up beginners. Study them carefully to avoid hours of debugging!

Using = instead of ==

main.c

if (a = 5) { }   // WRONG! This assigns 5 to a
if (a == 5) { }  // Correct! This compares a to 5

Integer Division Confusion

main.c

int result = 5 / 2;           // Result: 2, not 2.5!
float result = 5.0 / 2;        // Result: 2.5
float result = (float)5 / 2;   // Result: 2.5

Confusing & with &&

main.c

if (a & b) { }   // Bitwise AND (rarely intended)
if (a && b) { }  // Logical AND (usually intended)

11Try It Yourself

Here's a simple calculator that demonstrates arithmetic operators:

simple_calculator.c

1#include <stdio.h>
2
3int main() {
4    int a = 15, b = 4;
5    
6    // Arithmetic operators in action
7    printf("a = %d, b = %d\n\n", a, b);
8    printf("Addition:       a + b = %d\n", a + b);
9    printf("Subtraction:    a - b = %d\n", a - b);
10    printf("Multiplication: a * b = %d\n", a * b);
11    printf("Division:       a / b = %d\n", a / b);
12    printf("Modulus:        a %% b = %d\n", a % b);
13    
14    return 0;
15}

Expected Output:

a = 15, b = 4

Addition: a + b = 19
Subtraction: a - b = 11
Multiplication: a * b = 60
Division: a / b = 3
Modulus: a % b = 3

12Step-by-Step Precedence Solving

Understanding operator precedence is crucial for writing correct C code. Let's solve some complex expressions step-by-step.

Example 1: Arithmetic Precedence

result = 10 + 20 * 30 / 5 - 15

First, * and / (left to right): 20 * 30 = 600

10 + 600 / 5 - 15

Continue with /: 600 / 5 = 120

10 + 120 - 15

Now + (left to right): 10 + 120 = 130

130 - 15

Finally -: 130 - 15 = 115

result = 115

Example 2: Mixed Operators

result = 5 + 3 * 2 > 10 && 8 / 4 == 2

Arithmetic first (*, /): 3 * 2 = 6, 8 / 4 = 2

5 + 6 > 10 && 2 == 2

Then + : 5 + 6 = 11

11 > 10 && 2 == 2

Relational (>, ==): 11 > 10 = 1 (true), 2 == 2 = 1 (true)

1 && 1

Finally &&: 1 && 1 = 1 (true)

result = 1

Example 3: Assignment with Operations

int a = 5, b = 3;
result = a++ + ++b * 2

++b (pre-increment): b becomes 4, use 4

a++ + 4 * 2

Multiplication: 4 * 2 = 8

a++ + 8

a++ (post-increment): use 5, then a becomes 6

5 + 8

Addition: 5 + 8 = 13

result = 13, a = 6, b = 4

Precedence Quick Reference (High to Low)

Priority	Operators	Description
1 (Highest)	() [] -> .	Parentheses, array, member access
2	++ -- ! ~ sizeof	Unary operators (right to left)
3	* / %	Multiplication, division, modulus
4	+ -	Addition, subtraction
5	< <= > >=	Relational comparison
6	== !=	Equality comparison
7	&&	Logical AND
8	\|\|	Logical OR
9 (Lowest)	= += -= *= /=	Assignment (right to left)

When in doubt, use parentheses () to make your intention clear!

14Frequently Asked Questions

Q:What's the difference between = and ==?

= is the assignment operator — it puts a value into a variable: x = 5;

== is the equality operator — it compares two values and returns 1 (true) or 0 (false): if (x == 5)

Using = instead of == in conditions is one of the most common bugs in C!

Q:Why does 5 / 2 give 2 instead of 2.5?

When both operands are integers, C performs integer division, which truncates (cuts off) the decimal part.

To get 2.5, make at least one operand a float/double:

• 5.0 / 2 → 2.5
• 5 / 2.0 → 2.5
• (double)5 / 2 → 2.5

Q:When should I use && vs & (and || vs |)?

&& and || are logical operators — use them for conditions (if statements, loops).

& and | are bitwise operators — they work on individual bits of integers.

99% of the time, you want the double versions (&&, ||) for logic!

Q:What's the modulus operator (%) used for?

The modulus operator returns the remainder after division. Common uses:

• Check if even/odd: if (n % 2 == 0) → even
• Wrap around: index % arraySize → keeps index in bounds
• Extract digits: n % 10 → last digit
• Divisibility: if (n % 5 == 0) → divisible by 5

Q:What does the ternary operator ?: do?

It's a shorthand for if-else that returns a value:

condition ? value_if_true : value_if_false

Example: int max = (a > b) ? a : b;
This means: "If a > b, max is a; otherwise, max is b."

14Summary

What You Learned:

✓WHY: Operators let us perform math, compare values, and make decisions
✓Arithmetic: +, -, *, /, %, ++, --
✓Relational: ==, !=, >, <, >=, <=
✓Logical: &&, ||, !
✓Assignment: =, +=, -=, *=, /=, etc.
✓Precedence: *, / before +, - before comparisons before &&, ||

What You Will Learn

01Why Do We Need Operators?

Think About Math in Real Life...

Expression: 10 + 20

Types Based on Number of Operands

02Arithmetic Operators

Key Points for Beginners

Pre vs Post Increment

03Relational Operators

04Logical Operators

05Bitwise Operators

Visual: 5 & 3 (Bitwise AND)

Shift Trick

06Assignment Operators

07Other Operators

sizeof Operator - Getting Size in Bytes

08C Expressions

Expression vs Statement

09Operator Precedence

Quick Example

Full Tutorial Available

!Code Pitfalls: Common Mistakes & What to Watch For

Using = instead of ==

Integer Division Confusion

Confusing & with &&

11Try It Yourself

Expected Output:

12Step-by-Step Precedence Solving

Example 1: Arithmetic Precedence

Example 2: Mixed Operators

Example 3: Assignment with Operations

Precedence Quick Reference (High to Low)

14Frequently Asked Questions

Q:What's the difference between = and ==?

Q:Why does 5 / 2 give 2 instead of 2.5?

Q:When should I use && vs & (and || vs |)?

Q:What's the modulus operator (%) used for?

Q:What does the ternary operator ?: do?

14Summary

What You Learned:

Test Your Knowledge

Related Tutorials

Operator Precedence & Associativity

Type Casting & Type Conversion

Data Types & Variables

Have Feedback?

What You Will Learn

01Why Do We Need Operators?

Think About Math in Real Life...

Expression: 10 + 20

Types Based on Number of Operands

02Arithmetic Operators

Key Points for Beginners

Pre vs Post Increment

03Relational Operators

04Logical Operators

05Bitwise Operators

Visual: 5 & 3 (Bitwise AND)

Shift Trick

06Assignment Operators

07Other Operators

sizeof Operator - Getting Size in Bytes

08C Expressions

Expression vs Statement

09Operator Precedence

Quick Example

Full Tutorial Available

!Code Pitfalls: Common Mistakes & What to Watch For

Using = instead of ==

Integer Division Confusion

Confusing & with &&

11Try It Yourself

Expected Output:

12Step-by-Step Precedence Solving

Example 1: Arithmetic Precedence

Example 2: Mixed Operators

Example 3: Assignment with Operations

Precedence Quick Reference (High to Low)

14Frequently Asked Questions

Q:What's the difference between = and ==?