Primary Data Type In C Language

In the C programming language, there are three main categories of data types: primary, derived, and user-defined data types. In this article, we will focus only on the primary data types, also known as fundamental data types.

Primary Data Type

Primary data type are pre-defined, meaning they already exist in C programming language. Thes data type can be classify into types used for variable values and types used for constant values.

Table of contents :

Data type	Memory(byte)	Precision	Specifier
char	1	none	%c
int	4	none	%d
folat	4	6	%f
double	8	15	%lf

Data Types For Variable Values:

Syntax of variable primary data type :
type name = value ;

1 character and integer :

Primary data types character and integer can be written in two formats:

unsigned → to represent non-negative values, which can be only zero or postive numbers only.

signed→to represent both positive and negative values, including zero.

important notes:
- By default, all data types are signed, which means you do not need to write signed explicitly.
- To adjust the size or precision of a data type, you can use the long and short modifiers.

1.1) charachter :(Alpha Numerical) :

The char data type is used to store single characters.
Internally, each charcter is stored as integer value corresponding to its ASCII code  (for example, A = 65, B = 66, etc.).

 signed char : can store values from -128 to 127.

syntax code ;

We can declare a signed char variable in two ways:

- Declaration with initialization:

signed char name = 'value' ;

- Declaration first, then assignment:

signed char name ;

name = 'value' ;

example :

1.2)int :

The int data type is used to store integer numbers (whole numbers without decimal points).

signed int :  can store values from -2147483648  to 2147483647 (on a 4-byte system).

Syntax of the code :

We can declare an integer variable in two ways:

- Declaration with initialization:

signed int name = value ;

- Declaration first, then assignment:

int name ;

name = value ;

example :

unsigned int : The unsigned int data type is used to store non-negative integer values only.

Range: from 0 to  4294967295 (on a 4-byte system).

Syntax of the code :

-Declaration with initialization:

usigned int name = value ;

-Declaration first, then assignment:
unsigned int name ;
name = value ;

example :

1.3) long int : 

The long int data type is similar to int, but it can store larger integer values.

The main difference is in the size and syntax.

Signed long int → can store large positive and negative values (typically -2,147,483,648 to 2,147,483,647 on 4-byte systems, may be larger on 8-byte systems depending on the platform).

Unsigned long int → can store values from 0 to 4,294,967,295 (on a 4-byte system) .

1.4) long long  int : 

The long long int data type is used to store very large integer values. It is an extension of long int and typically takes 8 bytes in memory.

signed long long int : can store values from -9223372036854775808 to 9223372036854775807 .

Syntax of the code :

- Declaration with initialization: 

 long long int name = value ;

- Declaration first, then assignment:
long long name ;
name = value ;

example :

Unsigned long long int → can store values from 0 to 18,446,744,073,709,551,615.

Syntax of the code :

- Declaration with initialization:
unsigend long long name = value ;

- Declaration first, then assignment:
unsigned  long long name ;
naname = value ;

example :

2 float and double :

Float and double are data types in the C programming language used to store floating-point numbers (numbers with decimal points). 

They are used when we need to represent fractional values instead of whole numbers.

2.1) float :  

This is the second part of the variable data types. It is mainly used to store floating-point numbers. 

The float data type can store numbers with a range from 1.175494E−38 to 3.402823E+38, and it occupies 4 bytes in RAM.

Syntax of the code :

float name = value;     // declaration with initialization

or

float name;             // declaration

name = value;           // assignment

example :

2.2) double :

  if we need to more precision  we use this type because  it have precision  value up to 15 and his range is 2.225074E-308 to 1.797693E+308 and take 8 byte on RAM .

Syntax of the code :
or 
double name ;
name = value ;

double name = value ;

example :

2.3) long double :

precision ois 18 number and range of 3.4E-4932 to 1.1E+4932 but it take 12 byte on RAM .

Syntax of the code :
long double  name = value ;
or
long name ;
name = value ;
example  :

Data Types For Constant Values:

In C languages constants are the fixed values (not change) that never change during the execution of a program . It can have any data type , and there are two ways to define constant which is : #define preprocessor and const keyword .

1) #define :

This directive does not store into RAM but it used to replace every  insurance of label with text . and this text does not change at all  .

Syntax : 
#define  label text 
example :

Other example :

2) const :

This keyword is used to create constant  values . It work with all different primary data type , but it take as much space on mermory as any other variable .

Syntax :
const type name = value ;
example :

Note: the method of usage  of types or directives  on the memory of PC are not the same as when  we use it on Embedded  systems  . cause RAM of PC is very large than RAM of MCU , be carefull .