C----Study

1)  Numeric Data Types

Keyword           Variable Type               Range

char              Character (or string)       -128 to 127
int               Integer                     -32,768 to 32,767
short             Short integer               -32,768 to 32,767
short int         Short integer               -32,768 to 32,767
long              Long integer                -2,147,483,648 to 2,147,483,647
unsigned char     Unsigned character          0 to 255
unsigned int      Unsigned integer            0 to 65,535
unsigned short    Unsigned short integer      0 to 65,535
unsigned long     Unsigned long integer       0 to 4,294,967,295
float             Single-precision            +/-3.4E10^38 to +/-3.4E10^38
                  floating-point
                  (accurate to 7 digits)     
double            Double-precision            +/-1.7E10^308 to +/-1.7E10^308 
                  floating-point
                  (accurate to 15 digits)

 

C has really only four types of variables:

char int float double

1)enum

#include <stdio.h>

enum months { 
   JAN = 1, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC };

int main()
{ 
   enum months month; 

   const char *monthName[] = { "", "January", "February", "March", 
      "April", "May", "June", "July", "August", "September", "October",
      "November", "December" };
   
   for ( month = JAN; month <= DEC; month++ ) {
      printf( "%2d%11s\n", month, monthName[ month ] );
   } 

   return 0;
} 

 3) Union

Union has members of different data types, but can hold data of only one member at a time. The different members share the same memory location. The total memory allocated to the union is equal to the maximum size of the member.

#include <stdio.h>
union marks
{
    float percent;
    char grade;
};
int main ( )
{
    union marks student1;
    student1.percent = 98.5;
    printf( "Marks are %f   address is %16lu\n", student1.percent, &student1.percent);
    student1.grade = 'A';
    printf( "Grade is %c address is %16lu\n", student1.grade, &student1.grade);
}

4) Comparing the equality operator (==) with the '=' assignment operator.

 

a b a = b a == b 5 3 a = 3 (true) false 7 0 a = 0 (false) false 0 0 a = 0 (false) true

5) Register variable

 

Register variable is for faster access.

Register variable cannot be global variables.

#include <stdio.h>

main()
{
    register int i = 0;   

    for( i=0;i<2;i++)
    {
        printf("value of i is %d\n",i);
    }
}

6) Type conversion

 

1. Type conversion occurs when the expression has data of mixed data types.
2. In type conversion, the data type is promoted from lower to higher.
3. The hierarchy of data types: double, float, long, int, short, char.