What is the significance of the ‘volatile’ keyword in C?
a) It ensures a variable’s value is read from main memory, not from a CPU cache
b) It prevents a variable from being modified
c) It makes a variable thread-safe
d) It converts a variable to a constant
Answer:
a) It ensures a variable’s value is read from main memory, not from a CPU cache
Explanation:
The volatile keyword in C is used to indicate that a variable’s value can be changed at any time by something outside the control of the code section in which it appears, such as hardware or a different thread. When a variable is declared as volatile, the compiler does not optimize it, ensuring that its value is always read from main memory rather than being cached by the CPU. This is important in situations like memory-mapped peripheral registers, where the value might change independently of the program.
Understanding the volatile keyword is crucial for writing low-level, hardware-interacting, or multi-threaded C programs that require precise control over memory access.