A resource, or system resource, is any physical or virtual component of limited availability within a computer system. Every device connected to a computer system is a resource. Every internal system component is a resource. Virtual system resources include files

Computer file

A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...

, network connections and memory areas.

Major resource types

• CPU
  Central processing unit
  The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
  
   time
• Random access memory and virtual memory
  Virtual memory
  In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
  
  
• Hard disk
  Hard disk
  A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
  
   space
• Network throughput
• Electrical power
  Power management
  Power management is a feature of some electrical appliances, especially copiers, computers and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power state when inactive. In computing this is known as PC power management and is built...
  
  
• External Devices
  Peripheral
  A peripheral is a device attached to a host computer, but not part of it, and is more or less dependent on the host. It expands the host's capabilities, but does not form part of the core computer architecture....
  
  
• Input/output
  Input/output
  In computing, input/output, or I/O, refers to the communication between an information processing system , and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it...
  
   operations

Resource management

A resource handle is an identifier

Identifier

An identifier is a name that identifies either a unique object or a unique class of objects, where the "object" or class may be an idea, physical [countable] object , or physical [noncountable] substance...

 for a resource that is currently being accessed. Resource handles can be opaque, in which case they are often integer

Integer

The integers are formed by the natural numbers together with the negatives of the non-zero natural numbers .They are known as Positive and Negative Integers respectively...

 numbers, or they can be pointers that allow access to further information. Common resource handles are file descriptor

File descriptor

In computer programming, a file descriptor is an abstract indicator for accessing a file. The term is generally used in POSIX operating systems...

s and socket

Internet socket

In computer networking, an Internet socket or network socket is an endpoint of a bidirectional inter-process communication flow across an Internet Protocol-based computer network, such as the Internet....

s.

A situation when a computer program

Computer program

A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

 allocates a resource and fails to deallocate it after use is called a resource leak

Resource leak

In computer science, a resource leak is a particular type of resource consumption by a computer program where the program cannot release resources it has acquired. This condition is normally the result of a bug in a program...

. Resource tracking is the ability of an operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

, virtual machine

Virtual machine

A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...

 or other program to terminate the access to a resource that has been allocated but not deallocated after use. When implemented by a virtual machine this is often done in the form of garbage collection

Garbage collection (computer science)

In computer science, garbage collection is a form of automatic memory management. The garbage collector, or just collector, attempts to reclaim garbage, or memory occupied by objects that are no longer in use by the program...

. Without resource tracking programmers must take care of proper manual resource deallocation. They may also use the RAII technique to automate this task.

Access to memory areas is often controlled by semaphore

Semaphore (programming)

In computer science, a semaphore is a variable or abstract data type that provides a simple but useful abstraction for controlling access by multiple processes to a common resource in a parallel programming environment....

s, which allows a pathological situation called a deadlock

Deadlock

A deadlock is a situation where in two or more competing actions are each waiting for the other to finish, and thus neither ever does. It is often seen in a paradox like the "chicken or the egg"...

, when different thread

Thread (computer science)

In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...

s or processes

Process (computing)

In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...

 try to allocate resources already allocated by each other. A deadlock usually leads to a program becoming partially or completely unresponsive.

Access to resources is also sometimes regulated by queuing; in the case of computing time on a CPU

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

 the controlling algorithm

Algorithm

In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

 of the task

Task (computers)

A task is an execution path through address space. In other words, a set of program instructions that are loaded in memory. The address registers have been loaded with the initial address of the program. At the next clock cycle, the CPU will start execution, in accord with the program. The sense is...

 queue is called a scheduler

Scheduling (computing)

In computer science, a scheduling is the method by which threads, processes or data flows are given access to system resources . This is usually done to load balance a system effectively or achieve a target quality of service...

.

See also

• Computational resource
  Computational resource
  In computational complexity theory, a computational resource is a resource used by some computational models in the solution of computational problems....
  
  
• Resource (Web)
  Resource (Web)
  The concept of resource is primitive in the Web architecture, and is used in the definition of its fundamental elements. The term was first introduced to refer to targets of Uniform Resource Locators , but its definition has been further extended to include the referent of any Uniform Resource...
  
  
• Resource (Macintosh)
• Resource (Windows)
  Resource (Windows)
  In Microsoft Windows, resources are read-only data embedded in EXE, DLL, CPL or MUI files.The Windows API provides for easy access to all applications' resources.-Types:...
  
  
• Resource (Java)
  Resource (Java)
  In the Java programming language a resource is a piece of data that can be accessed by the code of an application.An application can access its resources through Uniform Resource Locators, like web resources, but the...
  
  
• Resource (Unix)