What is Asynchronous?

In a general context, asynchronous is an adjective that describes objects or events that are not coordinated in time. The term is from the Greek asyn, meaning not with, and chronos, meaning time. Asynchronous describes the relationship between two or more objects or events that interact within the same system but do not occur at fixed intervals. Because of this, these objects or events are not coordinated with each other, and they do not rely on each other’s existence to function. They have separate purposes.

Asynchronous meanings

In computing, asynchronous refers to data that is not synchronized when sent or received, meaning synchronization does not occur at regular or predetermined intervals. Asynchronous communication involves data that can be transmitted intermittently rather than in a steady stream. Since data is not transmitted at regular intervals, data is sent one byte or character at a time, and each byte is preceded by a start bit and stop bit. It doesn’t require the coordination or timing of bits between two endpoints. Unlike synchronous methods, asynchronous telecommunication does not use a clock signal, so sending data is not measured against a time reference.

Aside from computing, the term asynchronous has many meanings in the information technology (IT) field alone. Other applications of the term can apply to telecommunication, computer programming, data backup, workplace communication, and learning methods. The term’s uses will be outlined in more detail below.

As a real-life example, imagine an asynchronous telephone conversation between two people. Both parties can talk whenever they like; they are not required to wait a specific time or interval before speaking. If they did have to wait, it would be synchronous communication. Simply put, in synchronous communication, recipients must respond immediately. In asynchronous communication, they can respond at their convenience.

Uses of asynchronous in computing & communications

The adjective is used to describe processes in many fields. It’s worth noting the use cases listed below are not comprehensive, as there are many more applications of asynchrony.

Replication

Asynchronous replication is an approach to data backup and data protection that writes data to the primary storage array first, and then commits data to be replicated to memory or a disk-based journal. This data is then copied in real time or at scheduled intervals to replication targets.

Replication is not performed at the same time as changes are made in the primary storage. Data is replicated only in predetermined time periods, and it is not automatically updated in multiple locations. With asynchronous replication, network performance and availability are improved without affecting bandwidth.

Telecommunication

When communicating using devices such as radio or telephone, clarity of transmission is essential. Asynchronous Transfer Mode (ATM) is a network technology protocol based on transferring data in cells or packets of a fixed size. This allows asynchronous transmission of data without signals having to pass through a centralized clock. Clock synchronization is an internal synchronization approach that makes all clocks in network agree on the same value. Without having to pass through a centralized clock, data is transmitted intermittently rather than in a steady stream. Any timing required to recover data from the communication symbols is encoded within the symbols. ATM is used to guarantee a constant bit rate for telephone calls to ensure a caller’s voice is not cut off or delayed.

Advantages of asynchronous telecommunication

  • Devices can exchange information at their own pace. There is more flexibility in responding.
  • No complex processes are required of the receiving device, meaning the device can keep up with the data stream.
  • It doesn’t require 2-way communication to function.

Disadvantages of asynchronous telecommunication

  • Misunderstandings are more likely to happen.
  • Start and stop bits can be susceptible to line interference, meaning the transmission may not be successful.
  • A lot of the transmitted data is used for control and identification. Consequently, these bits of data carry no useful information, so more data packets have to be sent.

Workplace communication

In terms of human-to-human communication, asynchronous describes sending a message without expecting an immediate response. A simple example of asynchronous communication is sending an email and getting a response from the recipient several hours later. Neither party is required to be “present” at the same moment in time. Popular asynchronous communication tools include:

With the increase in remote work and online education, asynchronous communication keeps businesses, schools, and other organizations running smoothly, even though workers and students are not sharing the same space.

Programming

Asynchronous programming is a form of parallel programming that allows a unit of work to run separately from the primary application thread. These may be “outside” events such as the arrival of signals or actions instigated by a program that takes place simultaneously with program execution.

Asynchronous programming was designed to accommodate for the lag between when a function is called to when the value of that function is returned. Without it, applications would spend a long time on loading screens. Asynchronous functions are often found in front end applications and used in independent, high volume, input/output tasks. This type of programming is used in:

Learning

Asynchronous learning is a general term used to describe the form of education, instruction, or type of learning that does not occur in the same place or at the same time. It typically refers to online learning in which a student learns from instruction that is not being delivered in person or in real time.

While the course, instructor, or program will provide materials, lectures, assignments, and exams, they are accessed on one’s own schedule within a set deadline. Asynchronous learning can also encompass other instructional interactions including email exchanges between students and teachers, online discussion boards, and course-management systems that organize materials and correspondence.

Synchronous vs. asynchronous

With all five categories, synchrony serves as the contrast to asynchrony.

Replication

The primary difference between synchronous and asynchronous replication is the way data is written to the replica. Synchronous replication writes data to both the primary storage and the replica at the same time. This means the two remain synchronized at all times. Synchronous replication is commonly used when reliable and long-term storage is necessary and when it’s vital to not lose any data.

Asynchronous replication writes data to the primary storage first, and then copies that data to the replica. This type of replication tends to cost less than synchronous replication because synchronous requires more bandwidth and potentially specialized hardware. In addition, asynchronous replication is designed to work over long distances since the replication process is not required to occur in real time. A drawback of asynchronous replication is that the disaster recovery site might not contain the most recent changes made, so it’s possible critical data could be lost.

Telecommunication

Synchronous communication is a method in which a continuous stream of data signals is accompanied by a clock signal to ensure the transmitter and receiver are in sync. It transmits data in the form of chunks, while asynchronous communication transmits data one byte or character at a time. Synchronous communication requires a clock signal between transmitter and receiver to let the receiver know of the new byte. By contract, asynchronous communication does not need a clock signal because of the bits that are attached to the data being transmitted.

Asynchronous communication is slower than synchronous, and is more straightforward and cost-effective than its counterpart. Generally speaking, synchronous communication should be used for sending bulk amounts of data, while asynchronous communication should be used for sending small amounts of data.

Workplace communication

While asynchronous communication does not happen in real time, synchronous communication does. Synchronous communication is when a message is sent, and the recipient processes the information and responds immediately. An example of synchronous communication is an in-person meeting. When someone says something, the recipient receives the information said and immediately responds. The meeting attendees are in the same location at the same moment in time.

There are instances when synchronous communication is more beneficial than asynchronous. For example, if a team wants to brainstorm ideas for a project, face-to-face, real-time communication is better for bouncing ideas off one another and communicating concerns without fear of misinterpretation.

However, synchronous communication requires planning to ensure everyone on the team can meet at the same time. It also isn’t always necessary. It’s possible teams can brainstorm ideas via email chain or with a collaboration tool such as Slack. This way, team members are allowed to communicate ideas when it is convenient for them.

In some instances, asynchronous communication allows for more productive conversations. Emails are easier to remember and track than verbal conversations. In addition, email responses are often given more thought than a quick verbal response.

Programming

Synchronous programming follows a strict set of sequences. When code runs in a synchronous program, it will follow each step of an algorithm. It does so in order and will wait for the present operation to finish before continuing to the next. Asynchronous programming allows multiple processes to be started and allows these processes to run their course. When their job is finished, it gets the results and puts it through the necessary steps.

As a real-life example, we’ll use a waiter in a restaurant. An asynchronous waiter will come to a table, take their order, and give it to the kitchen. While the first table’s food is being prepared, the waiter will go to a different table, take their order, and give it to the kitchen. So the same waiter can serve many tables without waiting for the kitchen to prepare the first order. This is how asynchronous programming works.

In contrast, a synchronous waiter will be dedicated to just one table. He will take their order and deliver it to the kitchen. While the kitchen is preparing the table’s food, the waiter will not do anything else except wait to deliver the food. Once the food is ready, he will deliver it to the table. This is how synchronous programming works.

Learning

While asynchronous learning allows a student to work at their own pace and is more of a hands-off approach, synchronous learning happens in real time. This includes in-person classes or live online meetings in which classmates and the instructor interact in a specific virtual place at a set time. With this type of learning, instructors typically take attendance as they would in an in-person class. Methods of synchronous learning include video conferencing, live chatting, and in-person meetings.

There are programs that use a hybrid model, which incorporates both models of learning. If a student prefers active discussion, immediate feedback, and personal interaction, synchronous learning is best. Students can regularly interact with professors, allowing for face-to-face discussion and individual guidance. In contrast, if a student prefers learning when it is convenient for them, or if they have a demanding schedule, asynchronous learning is best. The student decides the pace at which they complete work and can work as fast or slow as they need to.

Advantages and disadvantages of asynchrony

In general terms, asynchrony allows for increased flexibility in the exchange of information and a release from having to be reliant on a time scale or logic for conversations. However, asynchrony can introduce a layer of complexity or delay that can sometimes complicate or obstruct the exchange of information.

UPDATED: This article was updated on April 6, 2021 by Web Webster.

 

Vangie Beal
Vangie Beal
Vangie Beal is a freelance business and technology writer covering Internet technologies and online business since the late '90s.

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