1. Operators

2. Precedence and Associativity of Operators
Operators Associativity
( ) [ ] . -> ++(postfix) --(postfix) left to right
++(prefix) --(prefix) ! ~ sizeof(type)
right to left
+(unary) -(unary) &(address) *(dereference)
* / % left to right
+ - left to right
<< >> left to right
< <= > >= left to right
== != left to right
& left to right
^ left to right
| left to right
&& left to right
|| left to right
? : right to left
= += -= *= /= %= >>= <<= &= ^= |= right to left
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3. Operators
 Comparison:
C operator Description Example
== = a == 2
!= Not equal a != 3
< < a<3
> > a>4
<=  a <= 5
>=  a >= 3
! Negative !(a < 3)
&& and (3 < a) && (a < 5)
|| or (a < 3) || ( 5 < a)
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4. Operators
 Arithmetic
Operator Description Example
+ + a+2
– – a–3
* * (Mutiplication) a*3
/ / (Division) a/4
% Remainder a%5
++ Increment a++, ++a
== Decrement a--, --a
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5. Operators
 Assignment
Operator Description Example
= assignment a=b
+= a=a+3 a += 3
-= a=a-3 a -= 3
*= a=a*3 a *= 3
/= a=a/3 a /= 3
%= a=a%3 a %= 3
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6. Increment and Decrement Operators
 Increment operator
Postfix k++
k = k - 1 ;
Prefix ++k
 Decrement operator
Postfix k--
 k = k - 1 ;
Prefix --k
But, It is a different when use with another operator
Prefix : increase or decrease before used in expression
Postfix : increase or decrease after used in expression
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7. Increment and Decrement Operators
[Ex] int i = 4, j;
j = ++i + 3;
printf(“i : %d, j = %dn”, i, j);
j = i++ + 3;
printf(“i : %d, j = %dn”, i, j);
j = --i + 3;
printf(“i : %d, j = %dn”, i, j);
j = i-- + 3;
printf(“i : %d, j = %dn”, i, j);
i = 5, j =8
i = 6, j =8
i = 5, j =8
i = 4, j =8
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8. Bit Operators
 <<, >>, |, &, ^,~
– << : Left shift n places
a = 100 << 1 ; 100 -> 01100100
printf( “%d”, a ) Shift to left by 1 bit
11001000 (=200)
– >> : Right shift n places
a = 100 >> 1 ; 100 -> 01100100
printf( “%d”, a ) Shift to right by 1 bit
001100100 (=50)
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9. Bit Operators
(8bit Computer)
 <<, >>, |, &, ^,~
– | : Logical OR, if either bit is 1, 100 -> 01100100
the result is 1 200 -> 11001000
a = 100 | 200 ; -------------------
printf( “%d”, a ) a = 11101100 (236)
– & : Logical AND, if both bits are 1,
100 -> 01100100
the result is 1
200 -> 11001000
a = 100 & 200 ; -------------------
printf( “%d”, a ) a = 01000000 (64)
– ^ : Logical XOR, if one and only
one bit is 1, the result is 1 100 -> 01100100
a = 100 ^ 200 ; 200 -> 11001000
printf( “%d”, a ) -------------------
a = 10101100 (172)
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10. Bit Operators
(8bit Computer)
 <<, >>, |, &, ^,~
– ~ : Logical inverter 100 -> 01100100
-------------------
a = ~100;
a = 10011011 (155)
printf( “%d”, a )
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11. Example
[Ex]
i = 3 , j = 2 , k = 1 ;
if ( i > j > k ) printf( “Yes” )
else printf( “No” ) ;
[Ex]
int a, i =1, j = 2, k ;
a = i < 2 + j;
j = 5 * (k = 3);
printf( “%d %d %dn”, a, i, j, k ) ;
( i < j ) && ( j < k )
This statement means that j is between i and k.
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12. Example
 Example
int a = 5, b = 6, c = 7 ;
int d ;
printf( “%d %d %dn, a < b, a > b, a != b ) ;
d = (a < b) && (b < c ) ;
printf( “%d %d %dn”, d, (a > b) || (b > c), !(!5) ) ;
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13. Assignment Operators
 Compound Assignment
– Compound Assignment operators
op= [Ex] *=, -=, /=, %=, +=
– variable = variable op (expression)
=> variable op= expression
[Ex] int k = 5;
k += 2; /* k = k + 2, k=7 */
k -= 2; /* k = k - 2, k=5 */
k *= 2; /* k = k * 2, k=10 */
k /= 2; /* k = k / 2, k=5 */
k %= 2; /* k = k % 2, k=1 */
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