For which data types can their contents be directly modified without using pointers?

In Go, you can directly modify the contents of the following variable types without using pointers:

• Primitive types: int, float64, bool, string (although strings in Go are immutable, you can assign new values)
• Arrays (if they are not passed by pointer)
• Structures (if they are not passed by pointer)

For example, if you have a variable of type int or a structure, you can change its fields or value directly:

var x int = 10
x = 20 // direct modification

type Point struct {
    X, Y int
}

p := Point{X: 1, Y: 2}
p.X = 5 // direct modification of the structure's field

Pointers are needed when you want to change the value of a variable passed to a function or work with large structures without copying.