The function of address characters in C language

Address symbol & is used in C language to: obtain the address of a variable and return a pointer value pointing to the memory location of the variable. By dereferencing a pointer, you can access the variable pointed to by the pointer. Pass the variable address so that the function can modify the variable outside the function. The address of an array element can be expressed as the array name plus an offset.

The role of the address character in C language

The address character (&) is a very important character in C language Important operator, it is used to get the address of a variable. The address of a variable is a pointer value that points to the memory location of the variable.

The function of the address character:

1. Get the variable address: & operator takes a variable as a parameter and returns the address of the variable. For example:

<code class="c">int x = 10;
int *ptr = &x;</code>

At this time, the value of ptr will be the address of the x variable.

2. Indirect access to variables: By dereferencing the pointer (* operator), you can access the variable pointed to by the pointer. For example:

<code class="c">int y = *ptr;</code>

At this time, y will get the value of the x variable (10).

3. Pass variable address: A function can get the variable address in its parameters, so that variables outside the function can be modified. For example:

<code class="c">void swap(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}</code>

This function exchanges the values ​​of two variables by getting the addresses of the a and b variables.

4. Array element address: The address of an array element can be expressed as the array name plus an offset. For example:

<code class="c">int arr[] = {1, 2, 3};
int *ptr = &arr[1];</code>

At this time, ptr will point to the second element of the array arr.

Notes on use:

You need to pay attention to the following aspects when using address characters:

• Null pointer: If the variable does not point to a valid memory address, the address character operation will cause undefined behavior.
• Pointer type: The returned address character type must be compatible with the variable type.
• Unmodifiable constants: The value of a constant variable cannot be modified through the address character.

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