Difference between int32 int int32 t int8 and int8 t

Question

I came across the data type int32 t in a C program recently   I know that it stores 32 bits  but don t int and int32 do the same   Also  I want to use char in a program   Can I use int8 t instead  What is the difference   To summarize  what is the difference between int32  int  int32 t  int8 and int8 t in C

User · Accepted Answer

Between int32 and int32 t   and likewise between int8 and int8 t  the difference is pretty simple  the C standard defines int8 t and int32 t  but does not define anything named int8 or int32 -- the latter  if they exist at all  is probably from some other header or library  most likely predates the addition of int8 t and int32 t in C99    Plain int is quite a bit different from the others  Where int8 t and int32 t each have a specified size  int can be any size    16 bits  At different times  both 16 bits and 32 bits have been reasonably common  and for a 64-bit implementation  it should probably be 64 bits    On the other hand  int is guaranteed to be present in every implementation of C  where int8 t and int32 t are not  It s probably open to question whether this matters to you though  If you use C on small embedded systems and or older compilers  it may be a problem  If you use it primarily with a modern compiler on desktop server machines  it probably won t be   Oops -- missed the part about char  You d use int8 t instead of char if  and only if  you want an integer type guaranteed to be exactly 8 bits in size  If you want to store characters  you probably want to use char instead  Its size can vary  in terms of number of bits  but it s guaranteed to be exactly one byte  One slight oddity though  there s no guarantee about whether a plain char is signed or unsigned  and many compilers can make it either one  depending on a compile-time flag   If you need to ensure its being either signed or unsigned  you need to specify that explicitly

User · Answer

The  t data types are typedef types in the stdint h header  while int is an in built fundamental data type  This make the  t available only if stdint h exists  int on the other hand is guaranteed to exist

User · Answer

Always keep in mind that  size  is variable if not explicitly specified so if you declare    int i   10    On some systems it may result in 16-bit integer by compiler and on some others it may result in 32-bit integer  or 64-bit integer on newer systems    In embedded environments this may end up in weird results  especially while handling memory mapped I O or may be consider a simple array situation   so it is highly recommended to specify fixed size variables  In legacy systems you may come across    typedef short INT16   typedef int INT32   typedef long INT64     Starting from C99  the designers added stdint h header file that essentially leverages similar typedefs   On a windows based system  you may see entries in stdin h header file as   typedef signed char       int8 t   typedef signed short      int16 t   typedef signed int        int32 t   typedef unsigned char     uint8 t    There is quite more to that like minimum width integer or exact width integer types  I think it is not a bad thing to explore stdint h for a better understanding

[c] Difference between int32, int, int32_t, int8 and int8_t

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