2.3. Processor operating modes

There are seven processor modes of operation:

User

The nonprivileged mode for normal program execution.

Fast interrupt (FIQ)

The privileged exception mode for handling fast interrupts.

Interrupt (IRQ)

The privileged exception mode for handling regular interrupts.

Supervisor

The privileged mode for operating system functions.

Abort

The privileged exception mode for handling Data Aborts and Prefetch Aborts.

System

The privileged user mode for operating system functions.

Undefined

The privileged exception mode for handling Undefined instructions.

Modes other than User mode are collectively known as privileged modes. Privileged modes are used to service exceptions or to access protected resources.

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