What are Primary Data Types?

Integer can be defined according to the size of the data and it can be modified further by using keyword unsigned and signed.  Default declaration is signed; that is a variable can store negative and positive data, to hole only positive data the variable can be changed to unsigned variable which will store only positive data twice its original size.  Therefore the size of the data to be stored in a variable depends on type of declaration.

int x:  The x store from -32768 to 32767 since by default it is a signed integer it can store positive and negative number within that range.

unsigned int x:  The x store from 0 to 65535 since it is declared as signed integer it can store only positive number within that range.

The data type can be declared unsigned for long, char,  small int, and int only.  The double and float can be signed data only.

Void data type is used to declare a generic pointer. 

void *gptr;

int *ptr;

gptr = ptr;

char *cptr

cptr = gptr;

Valid only in C

cptr = (char *)gptr;  In C++ type casting operator must be used to change the data type.

Note: In C void pointer can be assigned to non-void pointer without using cast. Where as in C++ cast operator must be used to assign void pointer to non-void pointer. 

Integer data types are of three types; octal, hexadecimal and decimal int x = 123; is decimal data type

int x = 0123; is octal data type int x = 0x12A; is hexadecimal

The primary data type like long, integer