What is Keyword in C programming language?
In C programming language a predefined set of reserved words provides computed control of various functions and declares in C compiler pre-processing libraries which perform special functions. The basic instructions are built up using a reserved set of words, for example main, for, if, else, switch, while, default, double, extern, for, and int, etc., Programming language C demands that they are used only for giving commands or making statements. The programmer cannot use the default, for example, as the name of a variable. An attempt to do so will result in a compilation error.
In formal keywords are standard forms of identifiers that have standard predefined meanings in the C compiler. Keywords are all lowercase since uppercase and lowercase characters are not equivalent because C programming supports Case sensitivity, So it’s possible to utilize an uppercase keyword as an identifier but it’s not a good programming practice.
Note:
- Keywords are the words whose meaning has already been explained to the C compiler and their meanings cannot be changed. Hence keywords are also called ‘Reserved words’.
- Keywords can be used only for their intended purpose.
- Keywords serve as basic building blocks for program statements.
- Keywords can’t be used as programmer defined identifier.
- The keywords can’t be used as names for variables.
- All keywords must be written in lowercase.
- 32 keywords available in C.
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Rules and Restrictions apply to keywords in C Programming Languages:
There have some predefined rules and restrictions that are followed by the developers about to initialize and used the keywords in C programming languages;
- Keywords are the words whose meaning has already been explained to the C compiler and their meanings cannot be changed.
- Keywords can be used only for their intended purpose.
- Keywords cannot be used as developer variables.
- All keywords must be written in lowercase.
List of standard keywords in C programming language :
| Data types | Qualifiers | User-defined | Storage Classes | Loop | Decision | Jump | Derived | function | Other |
| int | signed | enum | extern | for | if | goto | struct | void | const |
| char | unsigned | register | while | else | continue | union | return | volatile | |
| float | short | static | do | switch | break | sizeof | |||
| double | long | auto | case | ||||||
| default | |||||||||
Brief introduction of standard keywords and their specification:
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Data type Keywords:
| int | Specifies the integer type of value a variable will hold |
| char | Specifies the character type of value a variable will hold |
| float | Specifies the single-precision floating-point of value a variable will hold |
| double | Specifies the double-precision floating-point type of value a variable will |
Qualifier Keywords:
| signed | Specifies a variable can hold positive and negative integer type of data |
| unsigned | Specifies a variable can hold only the positive integer type of data |
| short | Specifies a variable can hold fairly small integer type of data |
| long | Specifies a variable can hold fairly large integer type of data |
Loop Control Structure Keywords
| for | Loop is used when the number of passes is known in advance |
| while | Loop is used when the number of passes is not known in advance |
| do | Loop is used to handle menu-driven programs |
User-defined type Keywords
| typedef | Used to define a new name for an existing data type |
| enum | Gives an opportunity to invent own data type and define what values the variable of this data type can take |
Jumping Control Keywords
| break | Used to force immediate termination of a loop, bypassing the conditional expression and any remaining code in the body of the loop |
| continue | Used to take control to the beginning of the loop bypassing the statements inside the loop |
| goto | Used to take control of required place in the program |
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