What type of devices are Personal Digital Assistants?

Personal Digital Assistants, commonly referred to as PDAs, are categorized as handheld computers. This classification is accurate as PDAs are compact, mobile devices designed for managing personal information, including contacts, calendars, and task lists. They operate on simple applications, allowing for quick and easy access to information on the go. PDAs are characterized by their portability, touch interfaces, and often, integration with cellular networks or internet connectivity for enhanced functionality.

Understanding the context of the other options helps highlight why handheld computers are the right classification for PDAs. Large mainframe systems are industrial-scale data processing machines designed for intensive computing tasks and not portable. High-performance desktops are powerful stationary computers aimed at demanding applications but also lack the mobility feature rooted in the nature of PDAs. Server-grade machines serve an entirely different purpose, focusing on processing requests and managing resources for networks and storage, and they are typically not handheld devices either. Thus, the distinctive feature of PDAs being handheld computers makes option B the correct choice.