Programmers use the volatile keyword in JavaScript to highlight the various fields which they can change by executing different threads subsequently. When a field is volatile, it means it cannot undergo any compiler optimization that is likely to happen through an individual thread access. This eliminates outdated values, and always displays the currently updated value on the field.

A programmer will use the volatile changer in the fields where numerous threads help access it, in the absence of the lock statement to grant access. There are different field types where the volatile keyword is applicable. They include:

  • Pointer types when they are in insecure context. Chances are, even when a pointer is volatile, the object it focuses on may not be. This means that programmers cannot claim a pointer to be volatile.

  • Reference types.

  • Enum types which have ushort, short, uint, int, sbyte, and byte as their foundation types.

  • Bool, char, float, uint, ushort, byte, sbyte, and short types.

  • UIntPtr and IntPr

  • Comprehensive type frameworks perceived to harbor reference type characteristics

A volatile keyword is applicable in structure or class fields. It is important to understand that programmers cannot confirm that local variables are volatile.

There are various procedures that happen during optimization. The just in time (JIT) compiler used in the CLR (Common Language Runtime) is likely to produce changeable results. This happens especially during execution of non-volatile data reads by the .Net program within a multiple threaded outline.

There are differences between non-volatile and volatile memory approach. What functions does the volatile keyword play? This article seeks to help the reader understand how and when to use the volatile keyword.

While there are various codes that explain this approach better, comprehending the functions of volatile keywords goes hand in hand with understanding the optimization and role of the Just In Time compiler in .Net.

What are JIT compiler optimizations?

Just in time compilation or dynamic translation refers to computer code execution. Here, compilation happens when programs go through execution at runtime as opposed to before the execution process. The process comprises of a bytecode or a source code. A byte code comes with interpretable instructions which move to the processor. Every time programmers write a JavaScript program, the Java compiler will accumulate the source language statements and convert them into byte codes. These have instructions that are similar to specific hardware processors, such as IBM system or Intel Pentium. A byte code refers to a sovereign code which can run on any platform.

The just in time compiler may alter the sequence of the writes and reads. This is present in the optimization process and does not result in altering a program’s output or meaning as shown below

x = 0;

x = 1;

Programmers can alter this code without changing the initial program’s syntax.

x = 1;

A programmer can use the just in time compiler to execute a constant propagation approach in optimizing the code shown below.

x = 1;

y = x;

Better still, programmers can alter the code without changing the initial program’s syntax to the following code

x = 1;

y = 1;

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Non-volatile vs. Volatile memory access

Technological advancements have revolutionized memory structures. Many programmers, especially newbies, have termed them as a little complex and confusing. They come with the principle memory that is communally used by various processors, different cache layers, and a processor register. Depending on different program execution, the processor is likely to cache the data. There are times when the executing thread requests this data.

The processor will, therefore, approach the data from within the cache and make it available. At this point, different executions will take place at varying intervals and times. For instance, the principal memory will not update immediately, and the data reads and updates do not run in correspondence with the cached version. Multiple thread applications suffer from this kind of memory consumption structure. A thread will read an out of date data version in the principal memory if the process of thread interaction in the cache experiences interruption from another thread simultaneously reading that data.

Why does this happen? If a non-volatile object value undergoes an update, the resulting change effects in the executing cache’s thread, as opposed to the principal memory. Again, if volatile object values undergo an update the resulting change transmits in both the principal memory and the executing thread’s cache. A thread will update the cache and read an updated value after reading the volatile object’s value.

How to use a volatile keyword in C#

A volatile keyword communicates with the just in time compiler in order to make sure a variable’s value is not cached. This prevents the hardware, operating system, and the subsequently executing thread from changing it. By so doing, there will not be any data conflicts resulting from the compiler’s inability to utilize variable optimizations. Variables are likely to be susceptible to volatile writes and reads, once a programmer indicates them or objects as volatile.

Whether programmers write data on a non-volatile or volatile object, each memory writes in C# remains volatile. Data reading may come with uncertainty though. This is because, during non-volatile data reading, an up to date value may not result from thread execution. A thread is likely to get an updated value from a volatile object. Once a programmer uses a volatile keyword before a variable, they can term it as volatile.

Programmers are able to utilize a volatile keyword with all pointers, enum, and reference types. Additionally, they can utilize a volatile modifier with all short, byte, char, int, bool, and float types. Programmers should understand that they cannot term a local variable as volatile. Once they establish a reference object type as volatile, this refers to the pointer (an object used in a programming language) only as opposed to the item’s value.

In addition, the fact that a double variable’s size is 64 bits means it is impossible to declare them as volatile. This is because they come in bigger sizes in comparison to that of Word on X86 structures. What can a programmer do to convert a double variable into volatile? They can incorporate it within a class by building a wrapper class. While a volatile keyword is capable of securing the thread in varying occurrences, programmers may have to be wary before making it the ultimate quick fix for problems arising from the thread.

Even after declaring an object or a variable as volatile, programmers should remember that there will be times they will have to utilize the lock keyword or statement. In addition, the volatile keyword cannot replace the lock keyword. However, it plays a huge role in preventing conflicts between data, especially during situations where various threads attempt to approach similar data.


Programmers should understand that volatile focuses on the collection of reads and fences. It also discharges fences upon writes. Therefore, there is a probability of changing a read preceded by a write. In order to achieve the desired demeanor, programmers should use an entire fence complete with the lock system.

Do you have any questions or comments? Leave them in the comment section below.

Postado 18 novembro, 2017


Software Developer

Lucy is the Development & Programming Correspondent for She is currently based in Sydney.

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