1.It is a type of data which is used in the program.
2.There are many predefined data types in c library like int, char, float etc.
| Basic Type | Integer Type(int) | 
| Floating Type(float) | |
| Character Type(char) | |
| Derived Type | Pointer | 
| Array | |
| Structure | |
| Union | 
Integer Type:
| Data Type | Size in bytes | Range | 
| short | 2 | -32768 to +32767 | 
| int | 2 | -32768 to +32767 | 
| unsigned int | 2 | 0 to 65536 | 
| long | 4 | -2147483648 to +2147483647 | 
| unsigned long int | 4 | 0 to 4,294,967,295 | 
Float Type:
| Data Type | Size in bytes | Range | 
| float | 4 | 3.4E-38 to 3.4E+38 | 
| double | 8 | 1.7E-308 to 1.7E+308 | 
| long double | 10 | 3.4E-4932 to 1.1E+4932 | 
Character Type:
| Data Type | Size in bytes | Range | 
| char | 1 | -128 to +127 | 
| signed char | 1 | -128 to +127 | 
| unsigned char | 1 | 0 to 255 |