What is a pointer and what happens if a function argument is a pointer?

In Go (Golang), a pointer is a variable that stores the address of another variable in memory. Instead of holding the value directly, the pointer points to the location where the value is stored.

If a function takes an argument of type pointer, it receives the address of the variable, not its copy. This allows the function to modify the value of the variable that the pointer points to directly.

Example:

func increment(num *int) {
    *num = *num + 1 // dereferencing the pointer and changing the value
}

func main() {
    a := 5
    increment(&a) // passing the address of variable a
    fmt.Println(a) // will output 6
}

Thus, using pointers in function arguments allows for efficient data modification without copying large structures and provides more flexible memory management.