Data Types and Qualifiers in C

There are four data types in C language. They are,

Types	Data Types
Basic data types	int, char, float, double
Enumeration data type	enum
Derived data type	pointer, array, structure, union
Void data type	void

Here we will discuss only basic data types.

Each variable in C has an associated data type. Each data type requires different amounts of memory and has some specific operations which can be performed over it. Let us briefly describe them one by one:

 

Following are the examples of some very common primitive data types used in C:

 

char: The most basic data type in C. It stores a single character and requires a single byte of memory in almost all compilers.

int: As the name suggests, an int variable is used to store an integer.

float: It is used to store decimal numbers (numbers with floating point value) with single precision.

double: It is used to store decimal numbers (numbers with floating point value) with double precision.

void:value less

Qualifiers are used to qualify the data type.The following are the qualifiers used with primitive data type.

 

unsigned, signed(default)

short,long

const

volatile

The unsigned qualifier avoids sign bit.

 

short and long :All store integers, but consume different memory and have different ranges. For eg: short int consumes 16bits, long int consumes 32bits and long long int consumes 64bits. The maximum value of short int is 32767. So of you need to store big values you need to use long int .

 

The qualifier const can be applied to the declaration of any variable to specify that its value will not be changed directly.Value of any variable can be changed either by program or external device.

 

The volatile qualifier is applied to a variable when we declare it. It is used to tell the compiler, that the value may change at any time. These are some properties of volatile.

The volatile keyword cannot remove the memory assignment
It cannot cache the variables in register.

The value cannot change in order of assignment.

Different data types also have different ranges upto which they can store numbers. These ranges may vary from compiler to compiler. Below is list of ranges along with the memory requirement and format specifiers on 32 bit gcc compiler.

Data Type             Memory(bytes)    Range              Format Specifier

short int                   2       -32,768 to 32,767                   %hd                   

unsigned short int          2       0 to 65,535                         %hu

unsigned int                4       0 to  4,294,967,295                 %u

int                         4      -2,147,483,648 to 2,147,483,647      %d or %i

long int                    4      -2,147,483,648 to 2,147,483,647      %ld

unsigned long int           4       0 to 4,294,967,295                  %lu

long long int               8       -(2^63) to (2^63)-1                 %lld

unsigned long long int      8       0 to 18,446,744,073,709,551,615     %llu

signed char                 1       -128 to 127                         %c 

unsigned char               1       0 to 255                            %c

float                       4       3.4E-38  to 3.4E+38                 %f

double                      8       1.7E-308 to 1.7E-30                 %lf

long double                12      3.4E-4932 to 1.1E+4932               %Lf

 

 

For windows ( 32 bit)

Data type- size in byte
char -1
short int -2
int -2
long int or long -4
float -4 (6 decimal places of precision)
double -8 (15 decimal places of precision)
long double -10 (19 decimal places of precision)

32-bit UNIX and Linux applications ( Solaris)Name Length

char 1 byte
short 2 bytes
int 4 bytes
long 4 bytes
float 4 bytes
double 8 bytes
long double 16 bytes

This shows that size depends on operating system and architecture ( 32 bit or 64 bit).We can use the sizeof() operator to check the size of a variable. See the following C program for the usage of the various data types:

#include <stdio.h>
int main()
{
int a = 1;
char b ='G';
double c = 3.14;
//printing the variables defined above along with their sizes
printf("character. value is %c and size is %lu byte.\n",b,sizeof(char));
printf(" integer. value is %d and size is %lu bytes.\n", a,sizeof(int));
printf(" double value is %lf and size is %lu ytes.\n",c,sizeof(double));
return 0;
}

 

The header file limits.h defines limits of integer types and the user can use the constants defined in it.
#include <limits.h>
#include <stdio.h>
int main()
{
printf("The max value of integer=%d",INT_MAX);
printf("The min value of integer=%d",INT_MIN);
return 0;
}

The header file float.h defines macros that allow you to use these values and other details about the binary representation of real numbers in your programs. The following example prints the storage space taken by a float type and its range values

#include <stdio.h> #include <float.h>

int main()

{

printf("Storage size for float : %d \n", sizeof(float));

printf("Minimum float positive value: %E\n", FLT_MIN );

printf("Maximum float positive value: %E\n", FLT_MAX );

printf("Precision value: %d\n", FLT_DIG ); return 0;

}

 

Macro	Value	Description
CHAR_BIT	8	Defines the number of bits in a byte.
SCHAR_MIN	-128	Defines the minimum value for a signed char.
SCHAR_MAX	+127	Defines the maximum value for a signed char.
UCHAR_MAX	255	Defines the maximum value for an unsigned char.
CHAR_MIN	-128	Defines the minimum value for type char and its value will be equal to SCHAR_MIN if char represents negative values, otherwise zero.
CHAR_MAX	+127	Defines the value for type char and its value will be equal to SCHAR_MAX if char represents negative values, otherwise UCHAR_MAX.

 

 

MB_LEN_MAX	16	Defines the maximum number of bytes in a multi-byte character.
SHRT_MIN	-32768	Defines the minimum value for a short int.
SHRT_MAX	+32767	Defines the maximum value for a short int.
USHRT_MAX	65535	Defines the maximum value for an unsigned short int.
INT_MIN	-2147483648	Defines the minimum value for an int.
INT_MAX	+2147483647	Defines the maximum value for an int.
UINT_MAX	4294967295	Defines the maximum value for an unsigned int.
LONG_MIN	-9223372036854775808	Defines the minimum value for a long int.

 

LONG_MAX	+9223372036854775807	Defines the maximum value for a long int.
ULONG_MAX	18446744073709551615	Defines the maximum value for an unsigned long int.

 

 

LLONG_MIN	-9223372036854775808	Minimumvalue for a variable of type long long
LLONG_MAX	9223372036854775807	Maximum value for a variable of type long long
ULLONG_MAX	18446744073709551615 (0xffffffffffffffff)	Maximum value for a variable of type unsigned long long

  

FLT_MAX DBL_MAX LDBL_MAX	3.402823466e+38F 1.7976931348623158e+308 1.7976931348623158e+308	Maximum representable floating point number
FLT_MIN DBL_MIN LDBL_MIN	1.175494351e-38F 2.2250738585072014e-308 2.2250738585072014e-308	Minimum positive value

 

enumerated data types
The discussion can be found here https://cprogramktu.blogspot.com/2018/01/enumerated-data-type.html

arrays
The discussion can be found here https://cprogramktu.blogspot.com/2018/01/arrays.html

structure and unions
The discussions can be found here https://cprogramktu.blogspot.com/2018/01/structures-and-unions.html

pointers
The discussions can be found here https://cprogramktu.blogspot.com/2018/02/pointers.html

Summary: