This document discusses the four main parts of a computer system: hardware, software, data, and users. It defines each part and provides examples. It also describes the basic computer hardware components, including processing devices, memory devices, input/output devices, and storage devices. The document outlines the types of software, including system software and application software. It explains how data is stored in computers using binary numbers and organized into files. Finally, it states that users oversee the setup, maintenance and use of the computer system.