Qualifiers

Qualifiers

Qualifiers alters the meaning of base data type to yield a new data type.
Size qualifiers:
Size qualifiers alters the size of basic data type. The keywords long and short are two size qualifiers. For example:
long int i;

The size of int is either 2 bytes or 4 bytes but, when long keywords is used, that variables will be either 4 bytes of 8 bytes. Learn more about long keywords in C programming. If the larger size of  variable is not needed then, short keywords can be used in similar manner as long keyword.
Sign qualifiers:

Whether a variables can hold only positive value or both values is specified by sign qualifiers. keywords signed and unsigned are used for sign qualifiers.
unsigned int a;
// unsigned variable can hold zero and positive values only
It is not necessary to define variables using keyword signed because, a variables is signed by default. Sign qualifiers can be applied to only int and char data type. For a int variable of size 4 bytes it can hold data from -231 to 231-1 but, if that variable is defined unsigned, it can hold data from 0 to 232 -1.

Constant qualifiers

Constant qualifiers can be declared with keywords const. An object declared by const cannot be modified.
const int p=20;
The value of p cannot be changed in the program.

Volatile qualifiers:
A variables should be declared volatile whenever its value can be changed by some external sources outside program. keywords volatile is used to indicate volatile variable.

data type