Keywords and Identifiers
Last updated on July 27, 2020
C language Character Set #
In C language you can use the following characters. Alphabets
1 2 | a, b, c, ... z
A, B, C, ... Z
|
Digits
0,1,2,3,4,5,6,7,8,9
Special Symbols The following table shows some special characters used extensively in C.
| Character | Meaning |
|---|---|
+ |
Plus Sign |
- |
Minus Sign |
* |
Multiplication |
/ |
Division |
% |
Percent Sign or modulus operator |
() |
Parentheses |
{} |
Curly braces |
[] |
Square brackets |
= |
Equal Sign |
, |
comma |
; |
Semicolon |
: |
colon |
' |
Single quote |
" |
Double quote |
? |
Question mark |
. |
Period or dot symbol |
# |
Hash |
^ |
Caret symbol |
~ |
Tilde |
! |
Exclamation mark |
& |
ampersand |
| |
pipe character |
Escape Sequences #
Escape Sequences are used to print some special characters which can't be printed directly using the keyboard. For example, newline, tab, carriage return etc. An Escape Sequences consists of a backslash character (\\) followed by a particular escape character. The following table lists common escape sequences.
| Escape Sequence | Meaning | What it does ? |
|---|---|---|
\n |
newline | Moves the cursor to the beginning of the next line. |
\t |
tab | Moves the cursor to the next tab stop. |
\b |
backspace | Moves the cursor back by one space on the current line. |
\r |
carriage return | Moves the cursor to the beginning of the current line. |
\a |
bell(alert) | Produces a beep sound. |
\\ |
backslash | Prints the backslash () character. |
\0 |
null | \0 character denotes a null character. |
\' |
single quote | Prints the single quote (') character. |
\" |
double quote | Prints the double quote (") character. |
! newline (\n), backspace (\b), Carriage return (\r), tab (\t), space () are known as whitespace characters.
Keywords #
Keywords are some reserved words that C language use for denoting something specific. In C, Keywords are written in lowercase. C has only 32 Keywords.
Identifiers #
Identifiers are the words we use to name entities like variables, functions, array, structure, symbolic constant etc. The rules for naming identifiers are as follows:
- Identifiers must consist of alphabets, digits or underscores (
_) only. - The first character should be an alphabet or underscore (
_). - The identifier should not be a keyword.
- Identifiers can be of any length.
C is case-sensitive language so my_var and MY_VAR are two distinct identifiers. Some examples of valid identifiers: num , _address , user_name , email_1 Examples of invalid identifiers: 1digit – an identifier must not start with a number my var – an identifier must not contain a space character int – int is a keyword some# – pound (#) character is not allowed
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