APL (named after the book A Programming Language)[8] is a programming language developed in the 1960s by Kenneth E. Iverson. Its central datatype is the multidimensional array. It uses a large range of special graphic symbols[9] to represent most functions and operators, leading to very concise code. It has been an important influence on the development of concept modeling, spreadsheets, functional programming,[10] and computer math packages.[6] It has also inspired several other programming languages.[4][5][7] It is still used today for certain applications.[11][12]