What does --a mean in c++

The --a operator in C is a unary decrement operator, which decrements the value of variable a by 1. Divided into prefix operators and postfix operators, the former uses the value after decrement, and the latter uses the value before decrement.

The meaning of --a in C

In C, --a is A unary decrement operator that decrements the value of variable a by one.

Usage:

--a can be used as a prefix operator or a postfix operator:

• Prefix operator: --a First decrement a by 1, and then assign the result to a. For example:

<code class="cpp">int a = 5;
--a; // 结果为 a = 4</code>

• Postfix operator: a-- Return the value of a first, and then a Decrement by 1. For example:

<code class="cpp">int a = 5;
int b = a--; // 结果为 b = 5, a = 4</code>

Difference:

Prefix decrement and suffix decrement differ in the time used for variables:

• Prefix decrement: Use the decremented value.
• Suffix decrement: Use the value before decrement.

Example:

<code class="cpp">int a = 5;

cout << --a << endl; // 输出：4（前缀递减）
cout << a-- << endl; // 输出：4（后缀递减）
cout << a << endl; // 输出：3（后缀递减后）</code>

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