What\'s the Distinction Between Using the register Keyword and Declaring Variables Without It in C ?

Register Keyword in C

When working with variables in C , there are times when you may wonder about the difference between using the register keyword and simply declaring a variable without it. Let's delve into the distinction between the two:

What's the Purpose of the register Keyword?

The register keyword serves as a suggestion to the compiler that it should store the specified variable in one of the processor's registers rather than in memory. By doing so, the compiler can potentially improve performance by reducing the number of times the CPU has to access slower memory to retrieve the variable's value.

However, it's important to note that the compiler is not obligated to follow this suggestion. It may choose to disregard it entirely and store the variable in memory regardless, especially if it believes there are more critical factors affecting performance.

What Herb Sutter Says

According to Herb Sutter, a renowned C expert and author of "Effective C ," variables declared with the register keyword have the same semantics as those declared using the auto specifier. This means that the compiler is responsible for selecting the optimal storage location for the variable based on a variety of factors, including its scope, lifetime, and usage patterns.

Should You Use the register Keyword?

While using the register keyword can sometimes yield performance benefits, it's not a universal solution. It's generally recommended to avoid using it unless you have specific performance concerns and have measured the impact that using it has on the performance of your code. Blindly using the register keyword can lead to unnecessary code complexity and potential performance issues.

In summary, the register keyword is a hint to the compiler that you'd like a particular variable to be stored in a register, but the compiler is free to do as it pleases and store it in memory if it deems that to be a better alternative.

The above is the detailed content of What\'s the Distinction Between Using the register Keyword and Declaring Variables Without It in C ?. For more information, please follow other related articles on the PHP Chinese website!