# control register

> processor register which changes or controls the general behavior of a CPU

**Wikidata**: [Q5165884](https://www.wikidata.org/wiki/Q5165884)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Control_register)  
**Source**: https://4ort.xyz/entity/control-register

## Summary
A control register is a processor register that alters or controls the general behavior of a CPU. It belongs to the class of processor registers and is specifically designed to manage fundamental CPU operations and features.

## Key Facts
-   **Class:** Control register is a type of processor register.
-   **Subclass:** It is a subclass of processor register.
-   **Function:** Changes or controls the general behavior of a CPU.
-   **Facet:** Is a facet of operating systems.
-   **Same As:** Said to be the same as Control/Status Register.
-   **Freebase ID:** /m/0dqdhd
-   **Microsoft Academic ID:** 17371454 (discontinued)
-   **Wikipedia:** Available in languages: Catalan (ca), German (de), English (en), Ukrainian (uk).
-   **Sitelink Count:** 4 (counting Wikipedia links).
-   **Model-Specific Relation:** Related to x86 instruction set control registers for CPU features (as a model-specific register).

## FAQs
### Q: What is the primary purpose of a control register?
A: A control register alters or controls the general behavior of a CPU, managing fundamental operations and features essential for processor function.

### Q: How does a control register differ from a general processor register?
A: While all control registers are processor registers, they are specifically designed for managing CPU behavior, unlike general processor registers used for data storage or immediate computation.

### Q: What is the relationship between control registers and operating systems?
A: Control registers are a key component that operating systems interact with to manage and configure CPU resources and behaviors.

### Q: Are control registers specific to certain processor architectures?
A: While the concept is universal, specific control registers and their features (like model-specific registers in x86) are defined by the processor architecture's instruction set.

### Q: What is another name used for control registers?
A: Control registers are also referred to as Control/Status Registers.

## Why It Matters
Control registers are fundamental to CPU operation and system software interaction. They enable the fine-grained management of processor features, modes of operation (like privileged execution), memory handling, and interrupt response. Without control registers, the CPU would lack the programmability necessary for complex tasks, secure environments, and efficient resource management essential for modern operating systems and applications. They form the critical interface between software and low-level hardware control.

## Notable For
-   **Fundamental CPU Control:** Directly responsible for altering and controlling the general behavior of a CPU, distinguishing it from data registers.
-   **Operating System Interface:** Acts as a primary point of interaction for the operating system to configure and manage CPU resources and features.
-   **Architectural Specificity:** While the concept is universal, specific control registers are defined by the processor architecture's instruction set (e.g., x86 model-specific registers).
-   **Equivalence to Status Registers:** Recognized as functionally equivalent to Control/Status Register entities.

## Body
### Definition and Classification
-   A control register is a type of processor register whose function is to change or control the general behavior of a CPU.
-   It belongs to the class of processor registers, which are immediately accessible working storage available as part of a digital processor.
-   It is explicitly a subclass of processor register.

### Function and Purpose
-   The core function of a control register is to manage and configure fundamental aspects of CPU operation.
-   This includes setting processor modes, enabling or disabling features, controlling memory management units, and defining interrupt handling behavior.
-   They are critical for the CPU to perform its core tasks under the direction of software.

### Relationships
-   Control registers are a facet of operating systems, indicating their deep integration into system software.
-   They are related to model-specific registers, specifically referencing x86 instruction set control registers used for CPU features.
-   Control registers are said to be the same as Control/Status Register entities.

### Identifiers and Presence
-   Control registers have a Freebase ID: /m/0dqdhd.
-   A discontinued Microsoft Academic ID is associated with them: 17371454.
-   A dedicated Wikipedia entry exists titled "Control register".
-   This Wikipedia entry is available in four languages: Catalan (ca), German (de), English (en), and Ukrainian (uk).
-   The Wikipedia entry currently has 4 sitelinks.