Table 1: IRQL Symbolic and Numeric Definitions
| Symbolic Name | Purpose | Intel Level | Alpha Level |
| High Level | Highest interrupt level | 31 | 7 |
| Power Level | Power event | 30 | 7 |
| IPI Level | Interprocessor signal | 29 | 6 |
| Clock Level | Clock tick | 28 | 5 |
| Profile Level | Performance monitoring | 27 | 3 |
| Device Level | General device interrupts | 3-26 | 3-4 |
| Dispatch Level | Scheduler operations and deferred procedure calls (DPCs) | 2 | 2 |
| APC Level | Asynchronous procedure calls (APCs) | 1 | 1 |
| Passive Level | No interrupts | 0 | 0 |