The role of the `volatile` keyword in C language is to indicate that a variable's value can be changed externally at any time, even if it appears not to change from within the program itself. This tells the compiler not to optimize the variable, ensuring that every read or write operation on the variable directly accesses its memory location rather than using a cached value stored in a register. In practical terms, `volatile` is often used in scenarios such as multi-threaded programming, hardware registers (e.g., device drivers), or signal handlers where the value might be altered by an interrupt or other external factors outside the control of the main program flow.

The role of the `volatile` keyword in C:

The `volatile` keyword informs the compiler that the variable defined after it may change at any time. Therefore, in the compiled program, whenever it is necessary to store or read this variable, the data will be directly read from the variable's address. Without the `volatile` keyword, the compiler might optimize the read and write operations, potentially using a temporary value stored in a register. If another program modifies this variable, an inconsistency could occur. The following example illustrates this. In DSP development, it is often necessary to wait for a certain event to trigger, so programs like the following are frequently written:

(Here you can provide the corresponding example code if needed)

In summary, the `volatile` keyword ensures that the compiler does not apply optimizations that assume the variable's value remains unchanged between operations, which is particularly important in scenarios involving hardware registers, interrupts, or multi-threaded applications.