Copyright Goodheart-Willcox Co., Inc. 40 Computer Service and Repair What Is an Operating System? An operating system (OS) is the underlying software that provides a computer user with all the basic services of resource management on the machine, including a fi le system structure for data storage and a means of communicating with all the various computer hardware. Th e operating system controls input and output (I/O) from disk storage units, monitors, printers, memory, and other computer components. It is also the job of the operating system to make sure programs running on the computer do not interfere with each other when competing for system resources. In the early days of computing, before operating systems were devised, users had to write code for all of the common tasks. If you wanted to save data, you had to write the code that told your computer how to do so. Operating system software has evolved over the years. Th ink of the evolution of computer software and hardware as a group of inventors constantly building a better mousetrap. What is considered a leading-edge operating system one day may not be the next day. In fact, it will likely become obsolete only a few years later. Th e constant evolution of computers makes this concept confusing. Each operating system has its individual strengths and weaknesses. Th e core of any operating system is referred to as the kernel. Just as a plant buds and grows from a single seed or kernel, so does operating system software. Th e core program is enhanced by other software applications that refi ne the computer system. Associated with the core can be programs that provide for user interface style, security, and specialized fi le systems. Operating systems allow application software to communicate with the BIOS. Th e BIOS translates the application software requests into instructions the hardware can understand, as outlined in Figure 2-1. Users give instructions to the computer system via application software such as spreadsheets, word processors, or games. Th e user can also give instructions directly to the operating system. Th e operating system communicates with the BIOS, which then communicates with the computer hardware and peripherals. For laptops, desktops, and workstations, the main operating systems in use to- day are Microsoft Windows, Apple macOS, and Linux. Th e latter two are derivatives of the Unix operating system originally developed by Bell Labs in the late 1960s. 1002: 1.3, 1.7 TECH TIP A repair installation uses var- ious install media to overwrite an existing operating system that has become corrupt or damaged while keeping in- stalled applications, user fi les, and settings. 1002: 1.3 User Application Software Operating System Software BIOS Computer Hardware Goodheart-Willcox Publisher Figure 2-1 Operating systems allow application software to communicate with the BIOS, which translates application software requests into instructions the hardware can understand.