Identifiers in C

Identifiers are:-

constant

variables

keywords

Define constant:-

Any information is constant
data = information = constant
types of constant

primary:- integer,real,character

secondary:- they are made with the help of primary such as:- array,string,pointer,union,etc.

Define variables:-

variables are the name of memory location where we store data

variable name is any combination of alphabet,digit

the first letter cannot be a digit

Keywords:- keywords are the predefined or reserved words.In C there are 31 keywords.C is a case sensitive so use keyword in small alphabets.

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Type casting

type casting or type conversion allows us to convert one data types into another.for type casting cast operator is required. Syntax:-- (type)expression or value; Example: int f =9/4; //without type casting o/p=2 float f=(float)9/4; //with type casting o/p=2.3 Type conversion are of two types: 1)Implicit Type Conversion:- it is also known as automatic type conversion.When the type conversion is performed automatically by the compiler,such type of conversion is known as implicit type conversion. 2)Explicit Type Conversion:- the type conversion performed by the programmer is known as explicit type conversion.which is done by cast operator as above mentioned.

Recursion--

Definition:- when a function call itself is called recursion. note:- the problem which is solved by recursion is also solved by loops, but it is not necessary the problem solved by loops is also solved by recursion. Example:- Explanation:- 1) a fun function declared which takes argument and return value 2) main starts fun is called by passing 3 value 3)after calling fun definition starts, where check if a==1 no because a is 3, s=a+fun(a-1) means s=3+fun(2) from here fun function is again called now this body again execute now a is 2, so s=3+fun(2), fun(2) is replaced by 2+fun(2-1=1) i.e s=3+2+fun(1) again fun function is called... overall s=3+2+1=6, s is return this return value goes where fun function is called , where return value is stored in k, so k=6 now print is 6.

UNION

Definition:- Union is similar to structure, except it allows you to define the variable that share storage spaces.Defining a means creating a new data types. How use union:- when we create a structure by using struct keyword, now making a union we just replace the keyword struct with the keyword union , other syntax will be same. Difference between Structure and Union:- the only difference between them is in memory. NOTE:- union is used for low level programming but structure mostly used for high level programming. Program to access union:- """SHARE IT WITH YOUR FRIENDS IF HE DID NOT KNOW""""

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