Data types in C

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Data type: is used to define the type of data that a variable can hold. For example: An integer variable can hold integer type data, a character variable can hold character type data, a float variable can hold float type data etc.

For Example: int is a data type used to define integer type variables. int a here, a is a variable of int (integer) type. It can store numbers from -2,147,483,648 to +2,147,483,647. And the size of int is 4 bytes.

Note: every variable which is to be used in the program must be declared as what data type it is.

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C language has some set of predefined data types to handle various kinds of data that we can use in our program. These data types have different storage capacities.

C language supports different types of data types:

1. Primary or Primitive data types: These are fundamental data types in C namely integer (int), floating point (float), character (char), double and void. Primary is also known as built-in or pre-defined data types.
2. Derived data types: Array, pointer, and function.
3. User defined data type: This data types are nothing but primitive data types, but a little twisted or grouped together such as Structure, Union, Enum.

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Built-in or Primitive data type:

Primitive types are the most basic data types in c programming language. such as int, char, float, double, void. Primitive data types are also known as predefined data type or basic data types.

Note: The memory size of basic data types may change according to 32 bit to 64 bit operating system.

Let's see the list of pre-defined or basic data type.

1. Data type	Size	Range	Description
   char	1 byte	-128 to +127	A character
   int	2 or 4 byte	-32,768 to 32,767 or -2,147,483,648 to +2,147,483,647	An integer
   float	4 byte	1.2E-38 to 3.4E+38	Single precision floating point number
   void	1 byte		Void type stores nothing

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int (Integer type):

In C programming, int (stands for integer) is a keyword used to define integer type variables before to use in a program.

Size of int is 2 or 4 bytes (according to 32 bit or 64 bit operating system) Older system stored int as 2 bytes within a range of -32,768 to 32,767. But now it's takes up 4 bytes and can range from -2,147,483,648 to 2,147,483,67.

For Example: int is a data type used to define integer type variables. int a here, a is a variable of int (integer) type. It can store numbers from -2,147,483,648 to +2,147,483,647. And the size of int is 4 bytes.

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char (character type):

Any character value in C stores a singal character and requires a singal byte (1 byte) of memory in almost all compilers within a range -128 to 127.

For Example: char grade = 'A' where grade is defined as character type variable it can store any value of char type within char range as mentioned above.

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float double and long double type:

Real numbers are represented in C with keywords float, double and long double. float defines a singal precision floating point number that can store 1.2E-38 to 3.4E+38. Whereas double defines double precision floating point numbers that can store 2.3E-308 to 1.7E+308.

Precision: Number of digits after the decimal point is called precision. For example: 23.3456 has precision four and 23.34 has two precision. By default Float has 6 decimal digits of precision and double has 15 decimal digits of precision.

Example to define float type variables:

/*Float has 6 decimal digits of precision */
 float average = 89.330000
  
/*Float has 6 decimal digits of precision */
 double percentage = 93.330000000000000

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void type:

In C programming, void means nothing, that means it does not store anything. It has different meaning in different places: When void is used as a function return type, it indicates that the function does not return a value. when void appears in a pointer declaration, it specifies that pointer is universal. When void is used in a function parameter list, it indicates that function takes no parameters.

For now you don't worry about void type, we will learn with example in later section of this programming tutorial.

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User defined data type:

Those data types which are defined or created by the user using primitive data type as per our need are known as user defined data types. For example: Structure, Union, and Enumeration.

Let's understand with a simple example how to create a user defined data type:

struct student{
  char name[50];
  int roll;
  float marks;
};

In above example, student is a new data type created by user with the help of primitive data types char, int and float.

Read more about-

• User defined data types: structure, union, enum
• Derived data types: array, function, pointer.

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