The two enum(s) in this code - what exactly are they doing? Why are they not simply defined as long or short? When I debug this status is 4 bytes. What is error_code datatype??
// make this VB compatible... #pragma pack (4) #ifndef IntVB #define IntVB short #endif typedef struct tagCommStatus { enum Comm status; enum CommErr error_code; IntVB nChannel; IntVB x_comm; IntVB y_comm; IntVB t_comm; IntVB z_comm; }CommStatus; status is a variable of type 'enum Comm' (or just Comm, if compiled as C++). error_code is a member variable of type 'enum CommErr'. You haven't included the code with the enum definitions, so it's hard to say for sure, although with names such as status and error_code, it's possible to take a guess.
In C, enums default to whatever size an integer is (i.e. probably 32bit on most platforms). In newer versions of C++, you can define the underlying data type for the enum if you wish, e.g.
enum Foo16 : int16_t { }; enum Foo8 : uint8_t { }; 
int. The enumeration constants are, but the type is not always. C 2018 6.7.2.2 4 says “Each enumerated type shall be compatible with char, a signed integer type, or an unsigned integer type. The choice of type is implementation-defined…”
statuscan only take on the values defined inenum Comm, which is defined elsewhere. Similarly, the membererror_codecan only take on the values defined inenum CommErr, which is also defined elsewhere. Yes, they could be replaced by a suitable integer type, but using theenumidentifies the possible legitimate values better than justintdoes. The size of anenumis up to the compiler — 4 bytes is a legitimate choice.