What is the 'volatile' qualifier?

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Shyam Shrivastava

In computer programming, the volatile qualifier is used to indicate to the compiler that a variable can be changed by some external entity that is not explicitly specified in the program. It is primarily used when working with multi-threaded or embedded systems where variables can be modified by hardware,...
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In computer programming, the volatile qualifier is used to indicate to the compiler that a variable can be changed by some external entity that is not explicitly specified in the program. It is primarily used when working with multi-threaded or embedded systems where variables can be modified by hardware, interrupts, or other threads outside of the normal flow of program execution. The volatile keyword informs the compiler not to optimize access to the variable by caching its value in a register or by reordering memory accesses. This is because the value of a volatile variable can change at any time due to external factors that the compiler may not be aware of, so it needs to be re-read from memory every time it is accessed. Here's an example in C/C++: volatile int sensorValue; // Declare a volatile integer variable int main() { while (1) { // Read the volatile variable int reading = sensorValue; // Perform some operations with the reading // Compiler won't optimize away the reading } return 0;} read less
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In computer programming, the volatile qualifier is used to indicate to the compiler that a variable can be changed by some external entity that is not explicitly specified in the program. It is primarily used when working with multi-threaded or embedded systems where variables can be modified by hardware,...
read more
In computer programming, thevolatilequalifier is used to indicate to the compiler that a variable can be changed by some external entity that is not explicitly specified in the program. It is primarily used when working with multi-threaded or embedded systems where variables can be modified by hardware, interrupts, or other threads outside of the normal flow of program execution. Thevolatilekeyword informs the compiler not to optimize access to the variable by caching its value in a register or by reordering memory accesses. This is because the value of a volatile variable can change at any time due to external factors that the compiler may not be aware of, so it needs to be re-read from memory every time it is accessed. Here's an example in C/C++: volatile int sensorValue; // Declare a volatile integer variable int main() {while (1) {// Read the volatile variableint reading = sensorValue;// Perform some operations with the reading// Compiler won't optimize away the reading}return 0;} read less
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The volatile qualifier declares a data object that can have its value changed in ways outside the control or detection of the compiler (such as a variable updated by the system clock or by another program).
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