Size of common data types in C Language

In C, the size of common data types varies with operating systems, compilers, and other factors.

 1 # Include <stdio. h>
 2 # Include < Float . H>
 3  
 4   # Define Pr (x) printf ("% 11 S: % 2lu bytes \ n", # X, (unsigned long) sizeof (x ))
 5  
 6   Int Main ( Void )
 7 {
 8 Pr (size_t );
 9 Pr ( Void *);
 10 Pr ( Char );
 11 Pr ( Short );
 12 Pr ( Int );
 13 Pr ( Long );
 14 Pr ( Long   Long );
 15 Pr ( Float );
 16 Pr ( Double );
 17 Pr ( Long   Double );
 18 Printf ( "  \ N ---- dig ------- Epsilon ----------- min ----------- MAX \ n " );
 19 Printf ( "  Flt % 3d %-14E %-14E %-14E \ n  " , Flt_dig, flt_epsilon, flt_min, flt_max );
 20 Printf ( "  DBL % 3d %-14E %-14E %-14E \ n  " , Dbl_dig, dbl_epsilon, dbl_min, dbl_max );
 21 Printf ( "  Ldbl % 3d %-14le %-14le %-14le \ n " , Ldbl_dig, ldbl_epsilon, ldbl_min, ldbl_max );
 22 Printf ( "  ---- --- -------------- \ N  " );
 23     Return   0 ;
 24 }

ThisProgramRunning results in ideone.com are as follows (http://ideone.com/jH1dT ):

Size_t: 4 bytes void *: 4 bytes CHAR: 1 bytes short: 2 bytes INT: 4 bytes long: 4 bytes long: 8 bytes float: 4 bytes double: 8 byteslong double: 12 bytes ---- dig ------- Epsilon --------- min ----------- Max FLT 6 1.192093e-07 1.175494e-38 3.402823e + 38 DBL 15 minutes-16 minutes-308 bytes + 308 ldbl 18 minutes-19 minutes-4932 1.189731e + 4932 -------------------------------------------------
 

In fact, this is a 32-bit Linux operating system, and the compiler is GCC 4.3.4.

The running result of this program in opensuse 12.1 64-bit operating system is as follows (the compiler is GCC 4.6.2 ):

Size_t: 8 bytes void *: 8 bytes CHAR: 1 bytes short: 2 bytes INT: 4 bytes long: 8 bytes long: 8 bytes float: 4 bytes double: 8 byteslong double: 16 bytes ---- dig ------- Epsilon --------- min ----------- Max FLT 6 1.192093e-07 1.175494e-38 3.402823e + 38 DBL 15 minutes-16 minutes-308 bytes + 308 ldbl 18 minutes-19 minutes-4932 1.189731e + 4932 -------------------------------------------------
 

In the above results, long double is 16 bytes, but in fact its range and precision are the same as those of 12 bytes, it may be because of the consideration of alignment of the byte boundary in the 64-bit operating system.