noun
subscripting
Computing term for accessing elements by index, typically in arrays or strings.
配列の要素にアクセスするには添字指定を使います。
You use subscripting to access elements of an array.
添字 means 'subscript' or 'index', while 添字指定 is the act or concept of subscripting.
Compound of 添字 (subscript, index) and 指定 (specification, designation).