Register storage classes:
- Keyword: register
- Memory allocation: Inside CPU registers
- Scope: Within the block or method
Note: Register variable must be defined as local variable.
Auto v/s Register variables:
- “auto” variables get memory in RAM
- “register” variables get memory inside Registers.
- “Register” variables can access much faster than “auto” variables.
Note: Repeated variables in the logic must be defined as register variables. For example “Loop counters”
Can’t we declare all variables as register?
- No, Registers is a small memory area. Hence, we cannot store maximum number of variables into registers.
- Only local variables and repeated variables need to store into registers.
We cannot define register variables globally:
| #include<stdio.h> register int a=30; int main() { auto int a=10; printf(“In main : %d \n”, a); return 0; } |