C Tokens :
The smallest individual elements or units in a program are called Tokens. C has the following tokens.
- Identifiers
- Keywords
- String
- Constants
- Operators
1. Identifiers:
Identifiers are the names that are given to various program elements such as variables, symbolic constants, and functions.
Rules for defining an Identifiers:
- An identifier can only have alphanumeric characters (a-z , A-Z , 0-9) (i.e. letters & digits) and underscore( _ ) symbol.
- Identifier names must be unique.
- The first character must be an alphabet or underscore.
- You cannot use a keyword as identifiers.
- Only the first thirty-one (31) characters are significant.
- Must not contain white spaces.
- Identifiers are case-sensitive.
Example :
some legal identifiers:
float _number;
float a;
int this_is_a_very_detailed_name_for_an_identifier;
-This type of identifier you should use in your programming.
The following are illegal identifiers:
float :e;
float for;
float 9PI;
float .3.14;
float 7g;
Float firstname
-This type of identifier you should not use in your programming (Not acceptable).
2. Keywords :
- Keywords are standard identifiers that have standard predefined meaning in C.
- Keywords are all lowercase, since uppercase and lowercase characters are not equivalent it’s possible to utilize an uppercase keyword as an identifier but it’s not a good programming practice.
Points to remember
1. Keywords can be used only for their intended purpose.
2. Keywords can’t be used as programmer-defined identifiers.
3. The keywords can’t be used as names for variables.
Keyword in c language:
- auto, double, int, struct, break, else, long, switch, case, enum, register, typedef, char, extern, return, union, etc.....
3. String
- Strings in c is an array of characters having null characters‘\0’ at the end of the string. Strings in c are enclosed in double-quotes(“”) and characters are enclosed in single-quotes('').
char a[5]={'1','2','3'};
char a[]="yash";
char a[5]="nishit";
char a[]="yash";
char a[5]="nishit";
4. Constants
- A character constant is a single character, enclosed in single quotation marks.
- e.g., ‘A’ ‘B’ ‘1’
For more click here:- Type of Constant
5. Operators
- The symbols which are used to perform logical and mathematical operations in a C program are called C operators.
- These C operators join individual constants and variables to form expressions.
- Operators, constants, and variables are combined together to form the expressions.
- Consider the expression A + B * 5.
Where, +, * are operators
5 is constant and
A + B * 5 is an expression.
For more click here:- Type of Operators
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