# user space

> software run under a kernel

**Wikidata**: [Q1142183](https://www.wikidata.org/wiki/Q1142183)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/User_space_and_kernel_space)  
**Source**: https://4ort.xyz/entity/user-space

## Summary
User space is a designated software environment where applications run under the supervision of a kernel. It functions as a specific layer of protection within computer systems, distinct from the privileged kernel mode. This environment is also commonly referred to as "userland" or "userspace."

## Key Facts
- **Definition:** User space is defined as software that is run under a kernel.
- **Classification:** It is a subclass of a "ring," which serves as a layer of protection in computer systems.
- **Relationship:** User space is the direct opposite of "kernel mode."
- **Context:** It functions as a facet of virtual memory.
- **Aliases:** The concept is also known as "userspace," "userland," and technically referred to as "User space and kernel space."
- **Global Reach:** The concept is documented across at least 10 Wikipedia language editions (including English, Spanish, French, and Japanese) and has a sitelink count of 22.
- **Identifiers:** It is tracked in the Google Knowledge Graph with the ID `/g/11fldsl6lz` and has a Freebase ID of `/m/0n5pp`.

## FAQs
### Q: What is the primary function of user space?
A: User space serves as the environment where software runs under a kernel. It acts as a protective layer in computer systems, separating standard software execution from critical system functions.

### Q: How does user space relate to kernel mode?
A: User space is the opposite of kernel mode. While user space handles standard software applications, kernel mode operates at a higher privilege level for system hardware access.

### Q: Is user space also known by other names?
A: Yes, user space is frequently referred to as "userspace" or "userland." In technical documentation comparing the two states, it is often labeled "User space and kernel space."

## Why It Matters
User space matters because it establishes the fundamental boundary between standard software applications and the critical core of an operating system. By defining a specific area where software runs under a kernel, this architecture provides a necessary layer of protection for the system. This separation ensures that processes in user space operate independently from the kernel mode, which manages hardware and system-critical functions.

This structural division is a subclass of a protection "ring," a concept essential for maintaining system stability and security. Without this distinction, user applications could directly interfere with kernel operations, leading to system crashes or security vulnerabilities. Additionally, user space is a facet of virtual memory, playing a key role in how modern systems manage and allocate memory resources to various applications. Its widespread recognition—evident through its presence across global languages and academic topics—highlights its status as a foundational element of computer science architecture.

## Notable For
- Being the designated environment for **software run under a kernel**.
- Acting as a **subclass of "ring"**, a key layer of protection in computer architecture.
- Being the direct **opposite of kernel mode**, defining the dual-state nature of modern operating systems.
- Functioning as a **facet of virtual memory**, integral to memory management.
- possessing significant global documentation with **22 sitelinks** and aliases in multiple languages including Japanese, French, and Spanish.

## Body

### Definition and Classification
User space is strictly defined as software run under a kernel. In the hierarchy of computer architecture, it is classified as a subclass of a "ring." A ring is described as a layer of protection in computer systems, placing user space within the security framework of the computer.

### Relationship to Kernel Mode
The concept is structurally defined by its opposition to "kernel mode." This relationship establishes the dichotomy found in operating systems where code runs either in the unprivileged user space or the privileged kernel space. This distinction is fundamental to the "User space and kernel space" concept documented in technical literature.

### Aliases and International Recognition
The entity is known by several distinct aliases, including "userspace" and "userland." It is also referred to as "Modo de usuario" (Spanish), "Mode utilisateur" (French), "ユーザースペース" and "ユーザーランド" (Japanese), and "内核空间" (Chinese).

### Identifiers and Metadata
User space is indexed under several major knowledge systems:
- **Wikidata:** It is associated with the description "software run under a kernel" and linked to the property "facet of" virtual memory.
- **Google Knowledge Graph:** ID `/g/11fldsl6lz`.
- **Freebase:** ID `/m/0n5pp`.
- **Microsoft Academic:** ID 2775877400 (discontinued).
- **Quora:** Topic "Userspace."

It maintains a Wikipedia presence with the title "User space and kernel space" across languages including Afrikaans, Arabic, Bengali, Bosnian, Catalan, Czech, English, Spanish, Farsi, and French.

## References

1. Freebase Data Dumps. 2013
2. Quora
3. [OpenAlex](https://docs.openalex.org/download-snapshot/snapshot-data-format)