Go normally copies a value when assigning it to another variable or passing it to a function. A pointer instead holds the memory address of a value of a specified type. It lets code share and, when appropriate, modify that value without copying the value itself. This is useful for large arrays and structs, and for methods that update receiver state. section 5.3 section 5.7
The type *int means “pointer to an int.” Use & to obtain a value’s address and * to dereference a pointer—to read or change the value at that address. A declared pointer’s zero value is nil, meaning it does not yet point to a value. section 3.7 section 3.7.1
Change a value through its pointer
count := 0 ptr := &count // ptr has type *int *ptr = 1 // count is now 1 Printing ptr shows its address; printing *ptr shows the int stored there. Assignment through *ptr changes the original value, not a separate copy. section 3.7 section 3.7.1
Pass an image array without copying it
type image4K [3840 * 2160]int func processPixels(pixels *image4K) { // Process the original array through pixels. } func main() { var pixels image4K processPixels(&pixels) } Go still passes the argument by value: the copied value is the pointer, not the entire array. Changes made to array elements through that pointer affect the original array. section 4.1.7
For a new struct, &person{name: "Andy", age: 42} creates a pointer while initializing its fields; new(person) creates a pointer to a zero-valued person. Use new(int) when a pointer to a new built-in value is needed. Choose a pointer when sharing, modification, or avoiding a substantial copy matters; otherwise, ordinary value copying keeps changes independent. section 3.7.2 section 5.3
