This article, authored by John D. Gould and Clayton Lewis, discusses the importance of user-centric design principles in creating useful and easy-to-use computer systems. The authors present three key principles: early and continual focus on users, empirical measurement of usage, and iterative design. These principles are contrasted with other design approaches, such as getting it right the first time or relying solely on design guidelines. The article also includes empirical data showing that these principles are not always intuitive to designers and explores the reasons why designers might not follow them. It further elaborates on the three principles, providing a methodology for design, and includes a successful case study of IBM's Audio Distribution System (ADS) to illustrate the application of these principles. The ADS example demonstrates how the principles can lead to significant advantages in system design.This article, authored by John D. Gould and Clayton Lewis, discusses the importance of user-centric design principles in creating useful and easy-to-use computer systems. The authors present three key principles: early and continual focus on users, empirical measurement of usage, and iterative design. These principles are contrasted with other design approaches, such as getting it right the first time or relying solely on design guidelines. The article also includes empirical data showing that these principles are not always intuitive to designers and explores the reasons why designers might not follow them. It further elaborates on the three principles, providing a methodology for design, and includes a successful case study of IBM's Audio Distribution System (ADS) to illustrate the application of these principles. The ADS example demonstrates how the principles can lead to significant advantages in system design.