- Call Us: +91 9188262375
- Email Us: info@conlinecourse.com
Register Storage Class in C Programming
Table of contents
-
Introduction
-
Turbo C++ IDE
-
A Basic C Program
-
Fundamentals
-
Input/Output Functions
-
Control Statements
-
Arrays
-
Strings
-
Functions
-
Storage Classes
-
Structure
-
Union
-
Pointers
-
Dynamic memory allocation
-
File
-
Graphics
-
The C Preprocessor
-
Standard Library Functions
-
ASCII Table
-
Examples
-
Questions and Answers
Register Storage Class
Physical storage space can be a variable that is the main storage. With access to the registers in the CPU is faster than main memory, a register variable to register the specified variable is the physical storage space of variables. However, they require that as much as possible to ensure the register, the register guarantee is not necessarily secure.
Register variables are stored in the register of the microprocessor. The number of variable which can be declared register are limited. This means that the variable has a maximum size equal to the register size. If more variables are declared as register variable, they are treated as auto variables. A program that uses register variables executes faster as compared to similar program without register variable.
To declare a variable register storage class register specified.
register int n;
Example for register variables :
In C programming, the `register` storage class is used to declare variables that should be stored in machine registers for faster access. However, the use of the `register` keyword is just a hint to the compiler, and it's up to the compiler whether to honor it or not. Here's a detailed overview of the `register` storage class in C:
Purpose of the `register` Storage Class:
- 1. Faster Access: Variables declared with the `register` keyword are stored in CPU registers instead of memory. Accessing data from registers is generally faster than accessing it from memory.
- 2. Optimization: By suggesting that a variable should be stored in a register, the programmer informs the compiler about the variable's importance and the potential performance benefits of faster access.
Syntax:
register int variable_name;
Characteristics of 'register' Variables:
- 1. Limited Availability: The number of available registers is limited, and the compiler decides which variables are assigned to registers based on optimization criteria.
- 2. No Direct Address: Since register variables are stored in CPU registers, they do not have a memory address. Therefore, you cannot use the address-of operator (`&`) to obtain the address of a register variable.
Example of 'register' Variables:
#include
int main() {
register int count;
for (count = 0; count < 1000000; count++) {
// Loop body
}
printf("Count: %d\n", count);
return 0;
}
Considerations:
- 1. Compiler Optimization: Modern compilers are highly optimized and may ignore the `register` keyword if they determine that storing a variable in a register does not improve performance.
- 2. Limited Usefulness: The usefulness of the `register` keyword has diminished over time with advances in compiler optimization techniques. Compilers are often better at optimizing code than manual hints provided by the programmer.
- 3. Portability: The behavior of the `register` keyword is implementation-dependent, meaning it may behave differently across different compilers and platforms.
When to Use 'register':
- 1. Critical Performance Code: Use the `register` keyword for variables that are heavily used in performance-critical sections of code, such as inner loops.
- 2. Profile-Guided Optimization: Use `register` variables based on profiling data to identify bottlenecks and hotspots in the code where faster access to variables may yield performance improvements.
Considerations for Modern C Programming:
- 1. Trust the Compiler: Trust the compiler's optimization capabilities, as it can often make better decisions about variable storage than manual hints provided by the programmer.
- 2. Focus on Algorithmic Optimization: Instead of micro-optimizations like using `register` variables, focus on algorithmic improvements and code design for better performance gains.
In summary, the `register` storage class in C is used to suggest to the compiler that a variable should be stored in CPU registers for faster access. While it may have been useful in the past, its usefulness has diminished with modern compiler optimization techniques. Use `register` variables judiciously in performance-critical code and rely on compiler optimizations for most cases.