Protected mode definition
Protected mode is an operational mode for x86-compatible central processing units (CPUs). It enables CPUs to access extended features like virtual memory, paging, and a higher range of addressable memory.
Compared to real mode, protected mode provides a more controlled and secure environment for executing programs by enforcing restrictions on how memory and hardware resources are accessed.
History of protected mode
- Introduction. In 1982, Intel introduced protected mode with the Intel 80286 (286) CPU.
- Enhancements. 1985 marked the introduction of the Intel 80386 (386) — a significant advancement in protected mode operation. The 386 could address up to 4 GB of memory and introduced virtual 8086 mode, allowing older software written for the 8086 to run in a virtualized environment within protected mode.
- Widespread adoption. Microsoft Windows and OS/2 were among the first to take full advantage of protected mode, offering better stability, security, and multitasking capabilities. It was a key factor in the transition from single-task operating systems, like MS-DOS, to the multitasking ones we use today, like Windows and Linux.
- Modern usage. Today, protected mode is the standard operational mode for all x86 processors in modern computers. It underpins the operation of all contemporary operating systems, providing a secure and stable environment for running complex applications and managing hardware resources.