C variable naming rules
Rules For Constructing Variable Name:-
- Characters Allowed :
- Underscore(_)
- Capital Letters ( A – Z )
- Small Letters ( a – z )
- Digits ( 0 – 9 )
- Blanks & Commas are not allowed
- No Special Symbols other than underscore(_) are allowed
- First Character should be alphabet or Underscore
- Variable name Should not be Reserved Word
Explanation with Example:-
Tip 1 : Use allowed Characters
Valid Names
num Num Num1 _NUM NUM_temp2
Tip 2 : blanks are not allowed
Invalid Names
number 1 num 1 addition of program
Tip 3 : No special symbols other that underscore
Valid Identifier
num_1 number_of_values status_flag
Tip 4 : First Character must be underscore or Alphabet
Valid Identifier
_num1 Num Num_ _ __
Invalid Identifier
1num 1_num 365_days
Tip 5 : Reserve words are not allowed
C is case sensitive.
However if we capitalize any Letter from Reserve word then it will become legal variable
name.
Valid Identifier
iNt Char Continue CONTINUE
Invalid Identifier
int char continue
Tip 6 : Name of Identifier cannot be global identifier
Basic Note :
Global predefined macro starts with underscore. (_) .We cannot use Global predefined macro as our function name.
Example : Some of the predefined macros in C
__TIME____DATE__
__FILE__
__LINE__
Valid Identifier
__NAME__ __SUM__
Invalid Identifier
__TIME__ __DATE__ __FILE__
Tip 7 : Name of identifier cannot be register Pseudo variables.
Invalid Example :
#include<stdio.h> int main(){ long int _AH = 15; printf("%ld",_AH); return 0; }
Tip 8 : Name of identifier cannot be exactly same as of name of another identifier within the scope of the function.
Valid Example :
#include<stdio.h> int main(){ int ivar = 15; { int ivar = 20; printf("%d",ivar); } return 0; }
Invalid Example : We cannot declare same variable twice within same scope
#include<stdio.h> int main(){ int ivar = 15; int ivar = 20; printf("%d",ivar); return 0; }
Remember following Tricks:-
- Do not Create unnecessarily long variable name
- Do not use underscore as first character to avoid confusion between System Variable & user defined variables because many system variables starts with undescore
- Variable names are case-Sensitive . i.e sum,Sum,SUM these all three are different variable names.
- Reserve words with one/more Capital letters allowed eg. Int,Float,chAr are allowed but try to skip them.
C variable naming rules
Reviewed by ANAND PANDEY
on
7:52:00 AM
Rating:
No comments: