Register Storage Class
- The variables defined as the register is allocated the memory into the CPU registers depending upon the size of the memory remaining in the CPU.
- We can not dereference the register variables, i.e., we can not use &operator for the register variable.
- The access time of the register variables is faster than the automatic variables.
- The initial default value of the register local variables is 0.
- The register keyword is used for the variable which should be stored in the CPU register. However, it is the compiler’s choice whether or not; the variables can be stored in the register.
- We can store pointers into the register, i.e., a register can store the address of a variable.
- Static variables can not be stored into the register since we can not use more than one storage specifier for the same variable.
Example 1
- #include <stdio.h>
- int main()
- {
- register int a; // variable a is allocated memory in the CPU register. The initial default value of a is 0.
- printf(“%d”,a);
- }
Output:
0
Example 2
- #include <stdio.h>
- int main()
- {
- register int a = 0;
- printf(“%u”,&a); // This will give a compile time error since we can not access the address of a register variable.
- }
Output:
main.c:5:5: error: address of register variable ?a? requested
printf("%u",&a);
