C Operators

Operator Categories Overview

Operators are symbols that perform actions on values. C has rich operator sets for arithmetic, comparison, logic, assignment, bitwise manipulation, pointers, and more.

Understanding precedence (which binds tighter) and associativity (left-to-right or right-to-left) is crucial for correct results. Note that some symbols have different meanings depending on context, e.g., unary '&' (address-of) vs binary '&' (bitwise AND).

Category	Operators	Examples
Arithmetic	+ - * / %	a+b a*b a/b a%2
Increment/Decrement	++ -- (prefix/postfix)	++i i--
Comparison	< <= > >= == !=	a
Logical	&& \|\| !	a&&b !flag
Assignment	= += -= *= /= %= <<= >>= &= ^= \|=	x+=2 x<<=1
Bitwise	& \| ^ ~ << >>	a&b a\|b a^b ~a a<<1
Ternary	?:	cond?x:y
Pointer/Member	& * . -> []	&x *p s.x ps->x arr[i]
Other	sizeof, (type)cast, , (comma)	sizeof(int) (double)x a=(b,c)

Arithmetic & Integer Division

/ between integers truncates toward zero; % gives the remainder (with the same sign as the dividend).

Use parentheses to make intent explicit and avoid precedence surprises.

Example

#include <stdio.h>
int main(void){
    printf("%d", 7/2);
    printf(" %d", 7%2);
    printf(" %.2f\n", 7/2.0);
    return 0;
}

Output

3 1 3.50

Prefix vs Postfix ++/--

Prefix increments then yields the new value; postfix yields the old value then increments.

Avoid expressions that modify and also read the same variable without sequencing (e.g., using multiple ++ on the same variable in one expression) — behavior can be undefined.

Example

#include <stdio.h>
int main(void){
    int i=3;
    printf("%d", ++i);
    i=3; printf(" %d\n", i++);
    return 0;
}

Output

4 3

Comparison and Logical (Short-Circuit)

Comparison operators produce an int result: 0 (false) or 1 (true). Logical && and || short-circuit: if the result is known from the left operand, the right operand is not evaluated.

Use short-circuit for null checks and guarding computations.

Example

#include <stdio.h>
int main(void){
    int x=0;
    if (x!=0 && (10/x)>1) { printf("won't print"); }
    printf("safe\n");
    return 0;
}

Output

safe

Logical vs Bitwise

Don't confuse logical operators with bitwise operators: '&&' and '||' operate on truth values and short-circuit; '&', '|', and '^' operate on individual bits and do not short-circuit.

Example

#include <stdio.h>
int main(void){
    unsigned a=0x5, b=0x2; // 0101 and 0010
    printf("%u ", a & b); // bitwise AND => 0000 0010 -> 2
    int p=0, q=1;
    printf("%d\n", p && q); // logical AND => 0
    return 0;
}

Output

2 0

Bitwise Operators (Masking and Shifts)

Bitwise operators operate on individual bits—useful for flags, embedded systems, and performance-sensitive code.

Shifts move bits left/right; be careful with shifting negative values (right shift of signed negatives is implementation-defined).

Example

#include <stdio.h>
int main(void){
    unsigned char flags = 0;
    const unsigned char READ=1u<<0, WRITE=1u<<1;
    flags |= READ;
    printf("%d ", (flags & READ)!=0);
    flags |= WRITE;
    printf("%d\n", (flags & WRITE)!=0);
    return 0;
}

Output

1 1

Pointers and Member Access

Unary '&' takes an address; unary '*' dereferences a pointer. Use '.' to access a struct member; use '->' when you have a pointer to a struct.

[] indexes an array (equivalent to *(base+index)).

Example

#include <stdio.h>
typedef struct { int x; } Point;
int main(void){
    Point p = { .x = 5 };
    Point *pp = &p;
    printf("%d %d\n", p.x, pp->x);
    return 0;
}

Output

5 5

Ternary, sizeof, Cast

Use cond ? a : b for concise conditional expressions (both arms should be compatible types).

sizeof yields the size in bytes at compile time; casting (type)expr converts the value to another type (may truncate).

Example

#include <stdio.h>
int main(void){
    int n=5; double d=(double)n/2;
    const char* s = (n%2==0) ? "even" : "odd";
    printf("%s %.1f %zu\n", s, d, sizeof(long));
    return 0;
}

Output

odd 2.5 8

The Comma Operator

The comma operator evaluates its left operand, discards the result, then evaluates and yields the right operand. It has the lowest precedence and left-to-right associativity. (This is different from commas used as separators in declarations/argument lists.)

Example

#include <stdio.h>
int main(void){
    int a=0, b=0;
    int r = (a=1, b=2, a+b);
    printf("a=%d b=%d r=%d\n", a, b, r);
    return 0;
}

Output

a=1 b=2 r=3

Precedence & Associativity Quick Reference

When in doubt, add parentheses for clarity.

Level (high→low)	Operators (grouped by precedence)	Associativity
Postfix	[] () . -> x++ x--	Left-to-right
Unary	++x --x + - ! ~ (type) * & sizeof	Right-to-left
Multiplicative	* / %	Left-to-right
Additive	+ -	Left-to-right
Shift	<< >>	Left-to-right
Relational	< <= > >=	Left-to-right
Equality	== !=	Left-to-right
Bitwise AND	&	Left-to-right
Bitwise XOR	^	Left-to-right
Bitwise OR	\|	Left-to-right
Logical AND	&&	Left-to-right
Logical OR	\|\|	Left-to-right
Conditional	?:	Right-to-left
Assignment	= += -= *= /= %= <<= >>= &= ^= \|=	Right-to-left
Comma	,	Left-to-right

C Operators

Operator Categories Overview

Operators are symbols that perform actions on values. C has rich operator sets for arithmetic, comparison, logic, assignment, bitwise manipulation, pointers, and more.

Category	Operators	Examples
Arithmetic	+ - * / %	a+b a*b a/b a%2
Increment/Decrement	++ -- (prefix/postfix)	++i i--
Comparison	< <= > >= == !=	a
Logical	&& \|\| !	a&&b !flag
Assignment	= += -= *= /= %= <<= >>= &= ^= \|=	x+=2 x<<=1
Bitwise	& \| ^ ~ << >>	a&b a\|b a^b ~a a<<1
Ternary	?:	cond?x:y
Pointer/Member	& * . -> []	&x *p s.x ps->x arr[i]
Other	sizeof, (type)cast, , (comma)	sizeof(int) (double)x a=(b,c)

Arithmetic & Integer Division

/ between integers truncates toward zero; % gives the remainder (with the same sign as the dividend).

Use parentheses to make intent explicit and avoid precedence surprises.

Example

#include <stdio.h>
int main(void){
    printf("%d", 7/2);
    printf(" %d", 7%2);
    printf(" %.2f\n", 7/2.0);
    return 0;
}

Output

3 1 3.50

Prefix vs Postfix ++/--

Prefix increments then yields the new value; postfix yields the old value then increments.

Avoid expressions that modify and also read the same variable without sequencing (e.g., using multiple ++ on the same variable in one expression) — behavior can be undefined.

Example

#include <stdio.h>
int main(void){
    int i=3;
    printf("%d", ++i);
    i=3; printf(" %d\n", i++);
    return 0;
}

Output

4 3

Comparison and Logical (Short-Circuit)

Comparison operators produce an int result: 0 (false) or 1 (true). Logical && and || short-circuit: if the result is known from the left operand, the right operand is not evaluated.

Use short-circuit for null checks and guarding computations.

Example

#include <stdio.h>
int main(void){
    int x=0;
    if (x!=0 && (10/x)>1) { printf("won't print"); }
    printf("safe\n");
    return 0;
}

Output

safe

Logical vs Bitwise

Don't confuse logical operators with bitwise operators: '&&' and '||' operate on truth values and short-circuit; '&', '|', and '^' operate on individual bits and do not short-circuit.

Example

#include <stdio.h>
int main(void){
    unsigned a=0x5, b=0x2; // 0101 and 0010
    printf("%u ", a & b); // bitwise AND => 0000 0010 -> 2
    int p=0, q=1;
    printf("%d\n", p && q); // logical AND => 0
    return 0;
}

Output

2 0

Bitwise Operators (Masking and Shifts)

Bitwise operators operate on individual bits—useful for flags, embedded systems, and performance-sensitive code.

Shifts move bits left/right; be careful with shifting negative values (right shift of signed negatives is implementation-defined).

Example

#include <stdio.h>
int main(void){
    unsigned char flags = 0;
    const unsigned char READ=1u<<0, WRITE=1u<<1;
    flags |= READ;
    printf("%d ", (flags & READ)!=0);
    flags |= WRITE;
    printf("%d\n", (flags & WRITE)!=0);
    return 0;
}

Output

1 1

Pointers and Member Access

Unary '&' takes an address; unary '*' dereferences a pointer. Use '.' to access a struct member; use '->' when you have a pointer to a struct.

[] indexes an array (equivalent to *(base+index)).

Example

#include <stdio.h>
typedef struct { int x; } Point;
int main(void){
    Point p = { .x = 5 };
    Point *pp = &p;
    printf("%d %d\n", p.x, pp->x);
    return 0;
}

Output

5 5

Ternary, sizeof, Cast

Use cond ? a : b for concise conditional expressions (both arms should be compatible types).

sizeof yields the size in bytes at compile time; casting (type)expr converts the value to another type (may truncate).

Example

#include <stdio.h>
int main(void){
    int n=5; double d=(double)n/2;
    const char* s = (n%2==0) ? "even" : "odd";
    printf("%s %.1f %zu\n", s, d, sizeof(long));
    return 0;
}

Output

odd 2.5 8

The Comma Operator

Example

#include <stdio.h>
int main(void){
    int a=0, b=0;
    int r = (a=1, b=2, a+b);
    printf("a=%d b=%d r=%d\n", a, b, r);
    return 0;
}

Output

a=1 b=2 r=3

Precedence & Associativity Quick Reference

When in doubt, add parentheses for clarity.

Level (high→low)	Operators (grouped by precedence)	Associativity
Postfix	[] () . -> x++ x--	Left-to-right
Unary	++x --x + - ! ~ (type) * & sizeof	Right-to-left
Multiplicative	* / %	Left-to-right
Additive	+ -	Left-to-right
Shift	<< >>	Left-to-right
Relational	< <= > >=	Left-to-right
Equality	== !=	Left-to-right
Bitwise AND	&	Left-to-right
Bitwise XOR	^	Left-to-right
Bitwise OR	\|	Left-to-right
Logical AND	&&	Left-to-right
Logical OR	\|\|	Left-to-right
Conditional	?:	Right-to-left
Assignment	= += -= *= /= %= <<= >>= &= ^= \|=	Right-to-left
Comma	,	Left-to-right

C Basics

C Functions

C Structures

C Enums

C Memory

C Quiz

C Operators

Operator Categories Overview

Arithmetic & Integer Division

Prefix vs Postfix ++/--

Comparison and Logical (Short-Circuit)

Logical vs Bitwise

Bitwise Operators (Masking and Shifts)

Pointers and Member Access

Ternary, sizeof, Cast

The Comma Operator

Precedence & Associativity Quick Reference

C Operators

Operator Categories Overview

Arithmetic & Integer Division

Prefix vs Postfix ++/--

Comparison and Logical (Short-Circuit)

Logical vs Bitwise

Bitwise Operators (Masking and Shifts)

Pointers and Member Access

Ternary, sizeof, Cast

The Comma Operator

Precedence & Associativity Quick Reference