C is structured oriented programming language it was developed at Bell Laboratories AT&T (American Telephone & Telegraph), located in U.S.A. by Dennis Ritchie in 1972.
It is also called as middle level language because it is used to develop application software and system software.
C support rich set of operators.
Initially C-language was developed for designing a compiler of UNIX-Operating System.
Founder of C Language
C’s character set
1. Alphabet A to Z
2. a to z
3. Special symbol ( ‘, < > , “ , ? ; - ; )
It is a name given to storage area and its value change during program execution.
It is used to store data , and its value change at any time.
Rules for defining variable
1. Variable name must start with alphabet and underscore.
2. Space are not allowed.
3. Keywords are not allowed.
4. Special symbol are not allowed.
5. Digits are allowed but first character must be alphabet or underscore.
6. Variable length should be 1 to 8 character long.
Syntax for variable declaration
Syntax:- type variable_name;
EX:- Example for declaring a variable.
here a, b are a variable and int , float are datatype .
There are five types of variable available in C they are given below.
a) local variable
b) global variable
c) static variable
d) automatic variable
e) external variable
Q> Why only underscore is allowed in variable declaration ?
Ans> There are following reason to used underscore.
1. Underscore is best and understandable if we used in any variable definition.
2. It provide understandable readable format.
3. It is the besst way to separate two names
These variables only exist inside the specific function that creates them. They are unknown to other functions and to the main program.
A variable that is declared outside the function or block or body is called global variable. If any function changes the value of the global variable so it will be changed for all.
It must be declared at the start of the block.
A variable that is declared with static keyword is called static variable.
It is declared at once and never changed before leaving the program.
All variables declared inside the block, are automatic variables by default. But we can also explicitly declare automatic variable using auto keyword.
We can share a variable in multiple C source files by using external variable. To declare a external variable, we need to use extern keyword.
It is a fixed entity which does not change during program execution.
Classification of C constant
It is a name given to variable, function, array, structure ,union etc.
It is a reserved keywords whose meaning allredy define in C compiler user can not change them.
C support 32 keywords.
It is a smallest unit of any expression like Variable, Constant, Keywords, String, Operators
Datatypes tells the which types of value hold by variable like as integer , float, char. C support three types of datatype
1.Primery datatype 2. User define datatype 3. Derived datatype.
Detail concept of dataypes their size, control string, range given below
Operator is a special symbol which perform arithmetic and logical operation. C support 8 types of operator they are given below.