[C Programming Language] C Simple Data Types

Primitive Data Types

C has five primitive data types :

1. int : used to define integer numbers


2. char : contains ASCII Code character (128 characters)


3. float : used to define floating point numbers


4. double : used to define big floating point numbers


5. bool : used to define two conditions --> true or false / 1 or 0

Example Variable Initialisation:

1. int
int tes;
tes = 5;

2. char
char answer = 'x';

3. float
float score = 85.3;

4. double
double height = 1,6782992;

5. bool
bool check = true;

Modifiers

The three data types above have the following modifiers.

• short


• long


• signed


• unsigned

The modifiers define the amount of storage allocated to the variable. ANSI has the following rules :

short int <= int <= long int
float <= double <= long double

Implicit specifier(s)	Explicit specifier	Bits	Bytes	Minimum value	Maximum value
signed char	same	8	1	−128	+127
unsigned char	same	8	1	0	255
char	one of the above	8	1	−128 or 0	+127 or 255
short	signed short int	16	2	−32,768	+32,767
unsigned short	unsigned short int	16	2	0	65,535
int	signed int	16 or 32	2 or 4	−32,768 or −2,147,483,648	+32,767 or +2,147,483,647
unsigned	unsigned int	16 or 32	2 or 4	0	65,535 or 4,294,967,295
long	signed long int	32	4	−2,147,483,648	+2,147,483,647
unsigned long	unsigned long int	32	4	0	4,294,967,295
long long	signed long long int	64	8	−9,223,372,036,854,775,808	+9,223,372,036,854,775,807
unsigned long long	unsigned long long int	64	8	0	18,446,744,073,709,551,615

Qualifier

1. Const

The const qualifier is used to tell C that the variable value can not change after initialisation.

For example, const float pi=3.14159;

So, the value of pi cannot be changed at a later time within the program.

Another way to define constants is with the #define preprocessor which has the advantage that it does not use any storage.

For example, #define PI 3.14159

2 . Volatile

volatile means the storage is likely to change at anytime and be changed but something outside the control of the user program. This means that if you reference the variable, the program should always check the physical address (ie a mapped input fifo), and not use it in a cashed way.

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