An operating system (OS) is system software that manages computer hardware and software resources, and provides common services for computer programs.

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it.

In the personal computer market, as of September 2023[update], Microsoft Windows holds a dominant market share of around 68%. macOS by Apple Inc.

In the mobile sector (including smartphones and tablets), as of September 2023[update], Android’s share is 68.92%, followed by Apple’s iOS and iPadOS with 30.42%, and other operating systems with.66%. Linux distributions are dominant in the server and supercomputing sectors.

Security-focused operating systems also exist. Some operating systems have low system requirements (e.g.

Others may have higher system requirements.

live CD) or flash memory (i.e. USB stick).

A single-tasking system can only run one program at a time, while a multi-tasking operating system allows more than one program to be running concurrently. This is achieved by time-sharing, where the available processor time is divided between multiple processes.

Multi-tasking may be characterized in preemptive and cooperative types. In preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs.

Cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking.

Single-user operating systems have no facilities to distinguish users but may allow multiple programs to run in tandem. A multi-user operating system extends the basic concept of multi-tasking with facilities that identify processes and resources, such as disk space, belonging to multiple users, and the system permits multiple users to interact with the system at the same time.

A distributed operating system manages a group of distinct, networked computers and makes them appear to be a single computer, as all computations are distributed (divided amongst the constituent computers).

They are designed to operate on small machines with less autonomy (e.g. PDAs).

Windows CE and Minix 3 are some examples of embedded operating systems.

A real-time operating system may be single- or multi-tasking, but when multitasking, it uses specialized scheduling algorithms so that a deterministic nature of behavior is achieved. Such an event-driven system switches between tasks based on their priorities or external events, whereas time-sharing operating systems switch tasks based on clock interrupts.

A library operating system is one in which the services that a typical operating system provides, such as networking, are provided in the form of libraries and composed with the application and configuration code to construct a unikernel: a specialized, single address space, machine image that can be deployed to cloud or embedded environments.[further explanation needed].

Basic operating system features were developed in the 1950s, such as resident monitor functions that could automatically run different programs in succession to speed up processing. Operating systems did not exist in their modern and more complex forms until the early 1960s.

When personal computers became popular in the 1980s, operating systems were made for them similar in concept to those used on larger computers.

Electronic systems of this time were programmed on rows of mechanical switches or by jumper wires on plugboards. These were special-purpose systems that, for example, generated ballistics tables for the military or controlled the printing of payroll checks from data on punched paper cards.

In the early 1950s, a computer could execute only one program at a time. Each user had sole use of the computer for a limited period and would arrive at a scheduled time with their program and data on punched paper cards or punched tape.

Programs could generally be debugged via a front panel using toggle switches and panel lights. It is said that Alan Turing was a master of this on the early Manchester Mark 1 machine, and he was already deriving the primitive conception of an operating system from the principles of the universal Turing machine.

Later machines came with libraries of programs, which would be linked to a user’s program to assist in operations such as input and output and compiling (generating machine code from human-readable symbolic code). This was the genesis of the modern-day operating system.

At Cambridge University in England, the job queue was at one time a washing line (clothesline) from which tapes were hung with different colored clothes-pegs to indicate job priority.[citation needed]. By the late 1950s, programs that one would recognize as an operating system were beginning to appear.

The first known example that actually referred to itself was the SHARE Operating System, a development of GM-NAA I/O, released in 1959. In a May 1960 paper describing the system, George Ryckman noted:.

One of the more famous examples that is often found in discussions of early systems is the Atlas Supervisor, running on the Atlas in 1962. It was referred to as such in a December 1961 article describing the system, but the context of “the Operating System” is more along the lines of “the system operates in the fashion”.

Brinch Hansen described it as “the most significant breakthrough in the history of operating systems.”. Through the 1950s, many major features were pioneered in the field of operating systems on mainframe computers, including batch processing, input/output interrupting, buffering, multitasking, spooling, runtime libraries, link-loading, and programs for sorting records in files.

In 1959, the SHARE Operating System was released as an integrated utility for the IBM 704, and later in the 709 and 7090 mainframes, although it was quickly supplanted by IBSYS/IBJOB on the 709, 7090 and 7094, which in turn influenced the later 7040-PR-150 (7040/7044) and 1410-PR-155 (1410/7010) operating systems.

During the 1960s, IBM’s OS/360 introduced the concept of a single OS spanning an entire product line, which was crucial for the success of the System/360 machines. IBM’s current mainframe operating systems are distant descendants of this original system and modern machines are backward compatible with applications written for OS/360.[citation needed].

When a process is terminated for any reason, all of these resources are re-claimed by the operating system.

So, what is computer memory, and why is it so important.

Without it and without access to it, a computer is just a useless box. From startup to shutdown, and all processes in between, a computer relies on several types of memory in order to function.

This diagram displays all inputs/outputs and processing pieces of a computer.

At the core of the computer is the central processing unit or CPU, the source of control that runs all programs and instructions. In order to function, computers use two types of memory: primary and secondary.

However, memory is not stored in the CPU, but the CPU would only be a mess of wires without it.

Nevertheless, if you had the memory of a computer, you would have a large capacity for forgetting information. That is because most computers make use of what is called random access memory (RAM).

To help you better understand this, imagine the following:. You are an expert gardener, except for one important drawback.

But when you wake up the next morning, you are asked to garden. At this command, all memories return, and you begin toiling.

The garden, the tools, seeds, etc., can be thought of as the secondary memory in this analogy.

While the terms ‘memory’ and ‘RAM’ are used interchangeably, the most common term used is random access memory or RAM, which is the data that contains instructions for processing computer operations: like the hapless gardener, the memory is used only for as long as the program needing it is running. Some of the reasons that a computer only needs the memory for processing include:.

An operating system (OS) manages all other applications and programs in a computer, and it is loaded into the computer by a boot program. It enables applications to interact with a computer’s hardware.

The kernel is the software that contains the operating system’s core components. To run other programmes, every computer has to have at least one operating system installed.

It is necessary to have at least one operating system installed in the computer to run basic programs like browsers.

Here is a list of some important features of operating systems: Now to perform the functions mentioned above, the operating system has two components:

It is the outermost layer of the OS and manages the interaction between user and operating system by: Shell provides a way to communicate with the OS by either taking the input from the user or the shell script.

For an in-depth understanding of this topic, check out this free operating system course. The kernel is the core component of an operating system for a computer (OS).

It serves as the primary interface between the OS and the hardware and aids in the control of devices, networking, file systems, and process and memory management. The kernel is the core component of an operating system which acts as an interface between applications, and the data is processed at the hardware level.

After that, the kernel provides and manages the computer resources and allows other programs to run and use these resources. The kernel also sets up the memory address space for applications, loads the files with application code into memory, and sets up the execution stack for programs.

Earlier, all the basic system services like process and memory management, interrupt handling, etc., were packaged into a single module in the kernel space. This type of kernel was called the Monolithic Kernel.

In a modern-day approach to monolithic architecture, a microkernel contains different modules like device management, file management, etc. It is dynamically loaded and unloaded.

Linus Torvalds introduced the concept of a monolithic kernel in 1991 as a part of the Linux kernel. A monolithic kernel is a single large program that contains all operating system components.

Monolithic Kernel As the name suggests, a monolithic kernel is a single large program that contains all operating system components. The entire kernel executes in the processor’s privileged mode and provides full access to the system’s hardware.

This type of kernel is generally used in embedded systems and real-time operating systems.

Microkernel A microkernel is a kernel that contains only the essential components required for the basic functioning of the operating system. All other components are removed from the kernel and implemented as user-space processes.

It is also more stable and secure than monolithic kernels.

Hybrid Kernel A hybrid kernel is a kernel that combines the best features of both monolithic kernels and microkernels. It contains a small microkernel that provides the essential components for the basic functioning of the OS.

This approach provides the best of both worlds, namely, the performance of monolithic kernels and the modularity of microkernels.

Exokernel An exokernel is a kernel that provides the bare minimum components required for the basic functioning of the operating system. All other components are removed from the kernel and implemented as user-space processes.

However, it is also the most difficult to implement and is not widely used. Now let’s look at the different types of operating systems.

In this section, we will discuss the advantages and disadvantages of these types of OS.

This OS does not directly interact with the computer. Instead, an operator takes up similar jobs and groups them together into a batch, and then these batches are executed one by one based on the first-come, first, serve principle.

Disadvantages of OS. Examples of Batch OS: payroll system, bank statements, data entry, etc.

In a distributed OS, various computers are connected through a single communication channel. These independent computers have their memory unit and CPU and are known as loosely coupled systems.

The major benefit of such a type of operating system is that a user can access files that are not present on his system but in another connected system. In addition, remote access is available to the systems connected to this network.

Disadvantages of Distributed OS. Examples of Distributed OS: LOCUS, etc.

This system provides access to a large number of users, and each user gets the time of CPU as they get in a single system. The tasks performed are given by a single user or by different users.

Advantages of Multitasking OS. Disadvantages of Multitasking OS.

Network operating systems are the systems that run on a server and manage all the networking functions. They allow sharing of various files, applications, printers, security, and other networking functions over a small network of computers like LAN or any other private network.

Advantages of Network OS. Disadvantages of Network OS.

Real-Time operating systems serve real-time systems. These operating systems are useful when many events occur in a short time or within certain deadlines, such as real-time simulations.

The hard real-time OS is the operating system for mainly the applications in which the slightest delay is also unacceptable. The time constraints of such applications are very strict.

The soft real-time OS is the operating system for applications where time constraint is not very strict. In a soft real-time system, an important task is prioritized over less important tasks, and this priority remains active until the completion of the task.

For Example, virtual reality, reservation systems, etc.

Disadvantages of Real-Time OS. Examples of Real-Time OS: Medical imaging systems, robots, etc.

It is a platform on which other applications can run on mobile devices. Advantages of Mobile OS.

Examples of Mobile OS: Android OS, ios, Symbian OS, and Windows mobile OS.

Some of the most popular operating systems in use today include: When choosing an operating system, there are several factors to consider, including:

Let’s explore these generations along with real-time examples: 1.

Second Generation: 3.

Fourth Generation: 5.

Sixth Generation (Speculative): 7.

These generations demonstrate how operating systems have evolved from basic machine-level instructions to sophisticated systems that can handle complex tasks and interactions with users. Each generation builds upon the achievements of the previous one, incorporating new technologies and capabilities.

We have listed some of them below:. There are several disadvantages of operating systems.

The kernel is a computer program at the core of a computer’s operating system and generally has complete control over everything in the system. The kernel is also responsible for preventing and mitigating conflicts between different processes.

A full kernel controls all hardware resources (e.g. I/O, memory, cryptography) via device drivers, arbitrates conflicts between processes concerning such resources, and optimizes the utilization of common resources e.g.

On most systems, the kernel is one of the first programs loaded on startup (after the bootloader). It handles the rest of startup as well as memory, peripherals, and input/output (I/O) requests from software, translating them into data-processing instructions for the central processing unit.

The critical code of the kernel is usually loaded into a separate area of memory, which is protected from access by application software or other less critical parts of the operating system. The kernel performs its tasks, such as running processes, managing hardware devices such as the hard disk, and handling interrupts, in this protected kernel space.

This separation prevents user data and kernel data from interfering with each other and causing instability and slowness, as well as preventing malfunctioning applications from affecting other applications or crashing the entire operating system. Even in systems where the kernel is included in application address spaces, memory protection is used to prevent unauthorized applications from modifying the kernel.

The kernel’s interface is a low-level abstraction layer. When a process requests a service from the kernel, it must invoke a system call, usually through a wrapper function.

There are different kernel architecture designs. Monolithic kernels run entirely in a single address space with the CPU executing in supervisor mode, mainly for speed.

MINIX 3 is a notable example of microkernel design. Instead, the Linux kernel is monolithic, although it is also modular, for it can insert and remove loadable kernel modules at runtime.

This central component of a computer system is responsible for executing programs. The kernel takes responsibility for deciding at any time which of the many running programs should be allocated to the processor or processors.

Random-access memory (RAM) is used to store both program instructions and data.[a] Typically, both need to be present in memory in order for a program to execute. Often multiple programs will want access to memory, frequently demanding more memory than the computer has available.

I/O devices include, but are not limited to, peripherals such as keyboards, mice, disk drives, printers, USB devices, network adapters, and display devices. The kernel provides convenient methods for applications to use these devices which are typically abstracted by the kernel so that applications do not need to know their implementation details.

Key aspects necessary in resource management are defining the execution domain (address space) and the protection mechanism used to mediate access to the resources within a domain. Kernels also provide methods for synchronization and inter-process communication (IPC).

Although the kernel must provide IPC in order to provide access to the facilities provided by each other, kernels must also provide running programs with a method to make requests to access these facilities. The kernel is also responsible for context switching between processes or threads.

The kernel has full access to the system’s memory and must allow processes to safely access this memory as they require it. Often the first step in doing this is virtual addressing, usually achieved by paging and/or segmentation.

Virtual address spaces may be different for different processes. the memory that one process accesses at a particular (virtual) address may be different memory from what another process accesses at the same address.

On many systems, a program’s virtual address may refer to data which is not currently in memory. The layer of indirection provided by virtual addressing allows the operating system to use other data stores, like a hard drive, to store what would otherwise have to remain in main memory (RAM).

When a program needs data which is not currently in RAM, the CPU signals to the kernel that this has happened, and the kernel responds by writing the contents of an inactive memory block to disk (if necessary) and replacing it with the data requested by the program. The program can then be resumed from the point where it was stopped.

Virtual addressing also allows creation of virtual partitions of memory in two disjointed areas, one being reserved for the kernel (kernel space) and the other for the applications (user space). The applications are not permitted by the processor to address kernel memory, thus preventing an application from damaging the running kernel.

To perform useful functions, processes need access to the peripherals connected to the computer, which are controlled by the kernel through device drivers. A device driver is a computer program encapsulating, monitoring and controlling a hardware device (via its Hardware/Software Interface (HSI)) on behalf of the OS.

Device drivers are an important and vital dependency for all OS and their applications. The design goal of a driver is abstraction.

In theory, a device should work correctly with a suitable driver. Device drivers are used for e.g.

At the hardware level, common abstractions of device drivers include:. And at the software level, device driver abstractions include:.

A kernel must maintain a list of available devices. This list may be known in advance (e.g., on an embedded system where the kernel will be rewritten if the available hardware changes), configured by the user (typical on older PCs and on systems that are not designed for personal use) or detected by the operating system at run time (normally called plug and play).

As device management is a very OS-specific topic, these drivers are handled differently by each kind of kernel design, but in every case, the kernel has to provide the I/O to allow drivers to physically access their devices through some port or memory location.

System calls provide the interface between a process and the operating system. Most operations interacting with the system require permissions not available to a user-level process, e.g., I/O performed with a device present on the system, or any form of communication with other processes requires the use of system calls.

A system call is a mechanism that is used by the application program to request a service from the operating system. They use a machine-code instruction that causes the processor to change mode.

This is where the operating system performs actions like accessing hardware devices or the memory management unit. Generally the operating system provides a library that sits between the operating system and normal user programs.

The library handles the low-level details of passing information to the kernel and switching to supervisor mode. System calls include close, open, read, wait and write.

Nowadays, computers are coming in various shapes and sizes and mostly fit everyone’s budgets. According to the definition of a computer–.

Also, the information processed is stored in a storage. With the advancement of technology, computers are becoming more and more advanced.

However, with the help of this article, we will try to understand the basic functions of computers that are performed by every computer irrespective of their shape and size.

Initially, when the user provides input to the computer from the input device the input data is stored in the primary memory then later the data is moved to the CPU(Central Processing Unit). When the data is at CPU it does the following tasks-.

As we know that computer is a data processing machine that doesn’t work until a set of information is given to the computer system via input devices. Any device that can be used by a user to instruct the computer is known as the input device.

Keyboard, Mouse, Joystick, etc. The input devices are responsible for getting data from the outside world and are in charge of processing this data for further execution.

In the case of manual data, it is generally fed through the mouse, keyboard, joystick, etc. In addition to this, the automated data is fed via a script, with the help of robots, etc.

Along with the primary input devices, other devices extract the data in various forms such as text audio-video, and images. For example, Webcams can be used to feed data in video or image form, microphones can be used to send data in the form of audio, etc.

This is the main function of a computer system. The raw data that is fed into the computer system vias input devices is processed here into meaningful data that is readable and understandable by the computer system.

To process this raw data the computer uses its CPU(Central Processing Unit) which is also known as the brain of the computer as it controls all the functions. i.e run scripts, control user commands, and many more.

This merger enhances the functionality and capabilities of computers in various ways.The Central Processing Unit consists of three main components that are:-. When the raw data supplied by the users is processed in the computer processor then its sent to the output devices by the CPU.

Various output devices are used to access different types of output data forms. ie.

The output received from the computer system can be stored in the form of soft copy and hard copy. Soft copy refers to the storing of processed data in the computer storage or other peripherals such as pen drives, hard disks which can be accessed later on the go.

printer. Various other output devices are-.

A computer stores data in the temporary memory which is known as RAM (Random Access Memory) whereas the information can be stored permanently both internally as well as externally. The data stored in a temporary memory can be erased during a sudden shutdown.

Various storage devices are used on a computer. Although, RAM, ROM, SSD/HDD plays a major role in the functioning of a computer system.

i.e Google Drive, MEGA, etc. With the advancement in technologies, computer functions are not limited.

The functionality of any computer mainly includes the following tasks. taking input data, processing the data, returning the results, and storing the data.

The central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions. 1.

Registers usually consist of a small amount of fast storage. 2 A CPU only has a small number of registers.

it is synonymous with the term “primary storage”. 3 The memory is much slower than the CPU register but much larger in size.

The CPU and the device controllers can execute in parallel, competing for memory cycles. To ensure orderly access to the shared memory, a memory controller is provided whose function is to synchronize the access to the memory.

In computing, input/output or I/O (or, informally, io or IO) is the communication between an information processing system, such as a computer, 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.

to “perform I/O” is to perform an input or output operation. 4.

Usually I/O operations does not make use of the CPU but are handled by the external devices. An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs.

In order to execute a program, the operating system must first create a process and make the process execute the program. At any point in time, the values of all the registers in the CPU defines the CPU context.

More generally, a task context is the minimal set of data used by a task (which may be a process or thread) that must be saved to allow a task to be interrupted, and later continued from the same point. 6.

In order to protect the operating system from user processes two modes are provided by the hardware: user mode and kernel mode.

This design allows the operating system kernel to execute with more privileges than user application processes. Synchronous means happening, existing, or arising at precisely the same time.

If an event occurs at the same instruction every time the program is executed with the same data and memory allocation, the event is synchronous. An synchronous event is directly related to the instruction currently being executed by the CPU.

Interrupts and exceptions are used to notify the CPU of events that needs immediate attention during program execution. Exceptions and interrupts are events that alters the normal sequence of instructions executed by a processor.

When an exception or interrupt occurs, execution transition from user mode to kernel mode where the exception or interrupt is handled. When the exception or interrupt has been handled execution resumes in user space.

A user program requests service from the operating system using system calls. System calls are implemented using a special system call exception.

The file system structure defines how information in key directories and files (existing and future) are organized and how they are stored in an operating system. Although different operating systems may have different standards, all major operating systems have similar characteristics and use a hierarchical structure of directories branching off the root directory.

The root directory, or “root”, is the highest-level directory of the file system structure. In macOS, Linux, and other UNIX-like operating systems, the root is represented with a forward slash (/).

The root contains all directories and files associated with a particular system or device. Under the root, there are some predefined subdirectories.

All other directories and files are located below the root. Directories, or folders, contain a list of the file names for each file in the directory.

Directories that are located inside other directories are called subdirectories. In hierarchical filesystems, the relationship between directories and subdirectories is sometimes described using a “parent”-”child” metaphor, where the “parent” directory is one level above the “child” directory.

A file’s location in the directory system is referred to as the file path and the file format, or type, determines how data in the file is created, stored, and read. The Filesystem Hierarchy Standard (FHS) is one example of a defined file system structure.

It is maintained by the Linux Foundation, and most Linux distributions follow the FHS. The FHS defines that all directories and files exist under the root.

Some examples of these files are included below: The purpose of using a defined file system structure like the FHS is so users and software can predict the locations of files and directories.

Operating systems are the glue that connects applications that do stuff we want and the hardware that allows us to do it (processors, hard drives, keyboards, etc.). This module contains a few exercises and links to explore how an operating system acts as this glue and the concept of a file which is at the heart of the operating system.

motorcycleExercise 1: Monitoring your computer’s Health and Functioning motorcycleExercise 2: Everything is a File (almost) motorcycleExercise 3: Creating your own tree-structured file system.

Explore the file system through both the graphical user interface and the command prompt and explain the connection between the two interfaces. Analyze the contents of files and directories and to determine the basic properties of each.

The operating system (OS) is often called the “platform” of a computer because it provides the resources that all software applications require to do their particular jobs. For example, a media player like VLC Player requires an operating system to retrieve sound files from the hard drive, send sound signals to the speakers, and receive instructions from the user.

Every operation we perform on a computer interacts with the computer’s operating system because the programs we use rely on the OS to interface with the hardware components.

The OS of a computer also manages which software is installed, where its files are located, and coordinates how the various programs which run on a computer can share resources such as the processor, the RAM, disk drives, and more. arrow_upward.

Understanding how these tools work will allow you to customize your computer’s settings, deal with malfunctioning programs, and use powerful software that requires system-level configurations. These exercise steps are designed for students with computers running the Microsoft Corporation’s proprietary Windows operating system.

This sequence will help you explore your operating system’s monitoring and coordination tools often called the “system monitor” or “task manager.” Because a computer can run many applications at the same time, the operating system is responsible for coordinating how those applications work together to use shared resources, such as the computer’s processor, memory, and hard drive space.

If you are following this tutorial as part of an online course, you should have been directed to create a word processing document to record your learning. Please create a heading for “Exercise 1” and record the following information based on your explorations:

A file is a named chunk of information in a computer that is created, stored, retrieved, and updated as a bundle. The operating system is responsible for tracking where each and every file in the system is located, coordinating access to those files, and allowing the user and programs to manipulate those files.

The video: Week 2, Segment 3 posted on YouTube will guide you though an exploration of the file tools available in operating systems. When done, then work through the following documentation steps.

You’ll be guided through locating the file properties dialog box and exploring the various features of the operating system’s file management tool set. This screen shot is of the properties dialog box for an image generated by the Windows screen Snipping application:

arrow_upward. Files in your system are stored in tree structures.

View the guide video embedded below: Week 2, Segment 4 for a walk through of this activity. The following steps will be also note how to document your tree-creation process.

Page created on 7 Feb 2018 and last updated on 7 Feb 2018 and can be freely reproduced according to the site’s content use agreement.

An accounting information system (AIS) involves the collection, storage, and processing of financial and accounting data used by internal users to report information to investors, creditors, and tax authorities. It is generally a computer-based method for tracking accounting activity in conjunction with information technology resources.

An accounting information system contains various elements important in the accounting cycle. Although the information contained in a system varies among industries and business sizes, a typical AIS includes data relating to revenue, expenses, customer information, employee information, and tax information.

An accounting information system must have a database structure to store information. This database structure is typically programmed with query language that allows for table and data manipulation.

In addition, accounting information systems are often highly secured platforms with preventative measures taken against viruses, hackers, and other external sources attempting to collect information. Cybersecurity is increasingly important as more and more companies store their data electronically.

The various outputs of an accounting information system exemplify the versatility of its data manipulation capabilities. An AIS produces reports including accounts receivable aging reports based on customer information, depreciation schedules for fixed assets, and trial balances for financial reporting.

However, correspondences, memos, or presentations are not included in the AIS because these items are not directly related to a company’s financial reporting or bookkeeping.

Within the system, the sales department can upload the sales budget. This information is used by the inventory management team to conduct inventory counts and purchase materials.

An AIS can also share information about a new order so that the manufacturing, shipping, and customer service departments are aware of the sale.

Policies and procedures can be placed within the system to ensure that sensitive customer, vendor, and business information is maintained within a company. Through the use of physical access approvals, login requirements, access logs, authorizations, and segregation of duties, users can be limited to only the relevant information necessary to perform their business function.