C - 演算子

演算子は、特定の数学関数または論理関数を実行するようにコンパイラに指示するシンボルです。 C言語には組み込み演算子が豊富で、次のタイプの演算子が用意されています。

- 算術演算子
- 関係演算子
- 論理演算子
- ビット演算子
- 代入演算子
- その他の演算子
この章では、各オペレータの作業方法を見ていきます。

算術演算子

次の表は、C言語でサポートされているすべての算術演算子を示しています。 変数Aが10を保持し、変数Bが20を保持し、

Operator	Description	Example
+	Adds two operands.	A + B = 30
−	Subtracts second operand from the first.	A − B = -10
*	Multiplies both operands.	A * B = 200
/	Divides numerator by de-numerator.	B / A = 2
%	Modulus Operator and remainder of after an integer division.	B % A = 0
++	Increment operator increases the integer value by one.	A++ = 11
--	Decrement operator decreases the integer value by one.	A-- = 9

関係演算子

次の表は、Cでサポートされているすべての関係演算子を示しています。変数Aが10を保持し、変数Bが20を保持し、

Operator	Description	Example
==	Checks if the values of two operands are equal or not. If yes, then the condition becomes true.	(A == B) is not true.
!=	Checks if the values of two operands are equal or not. If the values are not equal, then the condition becomes true.	(A != B) is true.
>	Checks if the value of left operand is greater than the value of right operand. If yes, then the condition becomes true.	(A > B) is not true.
<	Checks if the value of left operand is less than the value of right operand. If yes, then the condition becomes true.	(A < B) is true.
>=	Checks if the value of left operand is greater than or equal to the value of right operand. If yes, then the condition becomes true.	(A >= B) is not true.
<=	Checks if the value of left operand is less than or equal to the value of right operand. If yes, then the condition becomes true.	(A <= B) is true.

論理演算子

次の表に、C言語でサポートされているすべての論理演算子を示します。 変数Aは1を保持し、変数Bは0を保持し、次に -

Operator	Description	Example
&&	Called Logical AND operator. If both the operands are non-zero, then the condition becomes true.	(A && B) is false.
||	Called Logical OR Operator. If any of the two operands is non-zero, then the condition becomes true.	(A || B) is true.
!	Called Logical NOT Operator. It is used to reverse the logical state of its operand. If a condition is true, then Logical NOT operator will make it false.	!(A && B) is true.

ビット演算子
ビット単位の演算子はビット単位で動作し、ビットごとの演算を実行します。 ＆、|、^の真理値表は以下の通りです -

p	q	p & q	p | q	p ^ q
0	0	0	0	0
0	1	0	1	1
1	1	1	1	0
1	0	0	1	1

バイナリ形式でA = 60とB = 13と仮定すると、次のようになります。
A = 0011 1100
B = 0000 1101
-----------------
A＆B = 0000 1100
A | B = 0011 1101
A ^ B = 0011 0001
〜A = 1100 0011
次の表は、Cでサポートされているビット演算子の一覧です。変数 'A'は60を保持し、変数 'B'は13を保持し、

Operator	Description	Example
&	Binary AND Operator copies a bit to the result if it exists in both operands.	(A & B) = 12, i.e., 0000 1100
|	Binary OR Operator copies a bit if it exists in either operand.	(A | B) = 61, i.e., 0011 1101
^	Binary XOR Operator copies the bit if it is set in one operand but not both.	(A ^ B) = 49, i.e., 0011 0001
~	Binary Ones Complement Operator is unary and has the effect of 'flipping' bits.	(~A ) = -60, i.e,. 1100 0100 in 2's complement form.
<<	Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand.	A << 2 = 240 i.e., 1111 0000
>>	Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand.	A >> 2 = 15 i.e., 0000 1111

代入演算子
次の表は、C言語でサポートされている代入演算子の一覧です。

Operator	Description	Example
=	Simple assignment operator. Assigns values from right side operands to left side operand	C = A + B will assign the value of A + B to C
+=	Add AND assignment operator. It adds the right operand to the left operand and assign the result to the left operand.	C += A is equivalent to C = C + A
-=	Subtract AND assignment operator. It subtracts the right operand from the left operand and assigns the result to the left operand.	C -= A is equivalent to C = C - A
*=	Multiply AND assignment operator. It multiplies the right operand with the left operand and assigns the result to the left operand.	C *= A is equivalent to C = C * A
/=	Divide AND assignment operator. It divides the left operand with the right operand and assigns the result to the left operand.	C /= A is equivalent to C = C / A
%=	Modulus AND assignment operator. It takes modulus using two operands and assigns the result to the left operand.	C %= A is equivalent to C = C % A
<<=	Left shift AND assignment operator.	C <<= 2 is same as C = C << 2
>>=	Right shift AND assignment operator.	C >>= 2 is same as C = C >> 2
&=	Bitwise AND assignment operator.	C &= 2 is same as C = C & 2
^=	Bitwise exclusive OR and assignment operator.	C ^= 2 is same as C = C ^ 2
|=	Bitwise inclusive OR and assignment operator.	C |= 2 is same as C = C | 2

その他の演算子 sizeof とternary

上で説明した演算子の他に、sizeofや？などの他の重要な演算子がいくつかあります。 ：C言語でサポートされています。

Operator	Description	Example
sizeof()	Returns the size of a variable.	sizeof(a), where a is integer, will return 4.
&	Returns the address of a variable.	&a; returns the actual address of the variable.
*	Pointer to a variable.	*a;
? :	Conditional Expression.	If Condition is true ? then value X : otherwise value Y

Cでの演算子の優先順位
演算子の優先順位は、式の用語のグループ化を決定し、式の評価方法を決定します。 ある事業者は他の事業者よりも優先度が高い。 例えば、乗算演算子は、加算演算子よりも高い優先順位を有する。

例えば、x = 7 + 3 * 2; ここでは、operator *は+よりも高い優先度を持つため、xは13であり20ではないため、3 * 2で乗算されてから7に加算されます。

ここでは、優先順位が最も高い演算子が表の上部に表示され、最も低いものが下部に表示されます。 式の中で、優先順位の高い演算子が最初に評価されます。

Category	Operator	Associativity
Postfix	() [] -> . ++ - -	Left to right
Unary	+ - ! ~ ++ - - (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