The basics of computer hardware and software are presented. A computer is a general-purpose electronic counting device used in data processing because of its accuracy and high speed. The physical components of a computer system are called the hardware, which includes the central processing unit and peripheral equipment for data input, output, and storage. Computer capacity is measured by the amount of data that can be stored in main memory and by the computer word size. Performance is indicated by the speed with which instructions are executed. Input devices (e.g., keyboard-type terminals) are the components that accept raw data and convert it into electronic form, and output devices (e.g., video display terminals) present the results of data processing in human-readable form. System software is the set of instructions that facilitate hardware use and allow the application software, which solves specific user problems, to run efficiently. System and application software is written by using various machine and symbolic languages. Milestones in software-development techniques include program subroutine use, modular programming, functional decomposition, structured programming, and structured analysis. Objectives in improving software quality are reducing development costs, making maintenance easier, and making development results more predictable. Because software development has lagged behind revolutionary advances in hardware, the full potential of computers has yet to be realized.