C Keywords
C keywords, identifier in C, Rules for writing an identifier in C programming
Every C-word is classified as either a Keyword or an Identifier, Keywords are predefined words in a C compiler.
- There are 32 keywords in C language.
- Each keyword is meant to perform a specific function in a C program.
- All keyword have fixed meanings and these can not be changed.
- C keywords cannot be used as names of variables, names for functions or as user-defined Identifiers.
- All 32 C keywords are given below.
| Keywords in C |
| auto |
break |
case |
char |
| const |
continue |
default |
do |
| double |
else |
enum |
extern |
| float |
for |
goto |
if |
| int |
long |
register |
return |
| short |
signed |
sizeof |
static |
| struct |
switch |
typedef |
union |
| unsigned |
void |
volatile |
while |
Points about C Keywords
While using C keywords, always keep in mind the points listed below.
- C keywords are case sensitive.
- C Keywords are always written in lowercase.
- A C keyword can’t be use as name of variables / identifiers.
C Identifiers
Identifiers refer to the name of user-defined variables, functions, and arrays.
There are many types of computers, for example, a laptop, desktop, supercomputer but simply we call them like this is a computer. In the same manner for the name of the variable, array, function, structure, etc. we say that this is an identifier.
- These user-defined names consist of a sequence of letters and digits.
- Lower-case and upper-case letters, both are allowed.
- Underscore ( _ ) is also allowed.
- Generally, we use underscore as a link between two words in the long identifier for example user_Name.
In above example first_Number, second_Number, and result are called as identifiers.
Rules for writing an identifier
- The first character must be an alphabet or underscore.
- Only letters, digits or underscores are allowed.
- White space is not allowed.
- C keywords can not be used as identifiers.
- Maximum 31 numbers of characters are allowed in an identifier.