A smartphone's operating system differs from a PC's in several key aspects, primarily in terms of interface, functionalities, and resource management. Mobile OSs like iOS or Android are designed for touch interfaces and optimize for the limited hardware specifications of mobile devices. In contrast, PC operating systems, such as Windows or macOS, support more extensive multitasking capabilities and a wider range of applications. These differences impact how users interact with their devices and the types of software available, with mobile OSs focusing on apps designed for on-the-go usage.