Breaking down the design of a program into individual components (modules) that can be programmed and tested independently. It is a requirement for effective development and maintenance of large programs and projects.
Modular programming has evolved into object-oriented programming, which provides formal rules for developing self-contained software modules. See object-oriented programming
Building a program in modules, or independent routines, is common practice. The module performs a function and then returns control back to the program or instruction that called it. Modular programming has evolved into object-oriented programming, which provides stricter rules for developing self-contained routines.