What does the double equal sign mean in C language?

The double equal sign (==) in C language is a comparison operator, used to compare whether the values ​​​​of two expressions are equal, and return a Boolean value (0/1), indicating true or false. It can compare expressions of types such as numeric values, characters, pointers, and structures.

The meaning of double equal sign (==) in C language

The double equal sign (==) in C language ==) is a comparison operator used to compare whether the values ​​of two expressions are equal. The return result is a Boolean value, either 0 (false) or 1 (true).

Comparison operations

The double equal sign (==) is used to compare the values ​​​​of two expressions, including:

• Numeric types (Integers, floating point numbers, etc.)
• Character type
• Pointer type
• Structure type

Return result

If the values ​​of the two expressions are equal, the double equal sign returns 1 (true). Otherwise, returns 0 (false).

Example

int a = 10, b = 15;
char c = 'x', d = 'y';
int *p = &a, *q = &b;

if (a == b) {
    // a 和 b 相等
}
if (c == d) {
    // c 和 d 相等
}
if (p == q) {
    // p 和 q 指向同一个内存地址
}

Differences from other operators

Double equal sign (==) is different from other operators The following differences:

• Unlike the assignment operator (=), == is used to compare values, while = is used for assignment.
• Unlike the identity operator (===), == only compares values, while === compares both values ​​and types.
• Different from the inequality sign (!=), != is used to compare whether two expressions are equal.

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