Difference between long and int data types

Question

Considering that the following statements return 4  what is the difference between the int and long types in C     sizeof int  sizeof long

User · Accepted Answer

From this reference      An int was originally intended to be   the  natural  word size of the   processor  Many modern processors can   handle different word sizes with equal   ease    Also  this bit      On many  but not all  C and C     implementations  a long is larger than   an int  Today s most popular desktop   platforms  such as Windows and Linux    run primarily on 32 bit processors and   most compilers for these platforms use   a 32 bit int which has the same size   and representation as a long

User · Answer

The guarantees the standard gives you go like this   1    sizeof char   lt   sizeof short   lt   sizeof  int   lt   sizeof long   lt   sizeof long long    So it s perfectly valid for sizeof  int  and sizeof  long  to be equal  and many platforms choose to go with this approach   You will find some platforms where int is 32 bits  long is 64 bits  and long long is 128 bits  but it seems very common for sizeof  long  to be 4    Note that long long is recognized in C from C99 onwards  but was normally implemented as an extension in C   prior to C  11

User · Answer

A typical best practice is not using long int short directly  Instead  according to specification of compilers and OS  wrap them into a header file to ensure they hold exactly the amount of bits that you want  Then use int8 int16 int32 instead of long int short  For example  on 32bit Linux  you could define a header like this  typedef char int8  typedef short int16  typedef int int32  typedef unsigned int uint32

User · Answer

On platforms where they both have the same size the answer is nothing  They both represent signed 4 byte values     However you cannot depend on this being true   The size of long and int are not definitively defined by the standard   It s possible for compilers to give the types different sizes and hence break this assumption

User · Answer

You re on a 32-bit machine or a 64-bit Windows machine   On my 64-bit machine  running a Unix-derivative O S  not Windows   sizeof int     4  but sizeof long     8   They re different types     sometimes the same size as each other  sometimes not    In the really old days  sizeof int     2 and sizeof long     4     though that might have been the days before C   existed  come to think of it   Still  technically  it is a legitimate configuration  albeit unusual outside of the embedded space  and quite possibly unusual even in the embedded space

User · Answer

The long must be at least the same size as an int  and possibly  but not necessarily  longer   On common 32-bit systems  both int and long are 4-bytes 32-bits  and this is valid according to the C   spec   On other systems  both int and long long may be a different size   I used to work on a platform where int was 2-bytes  and long was 4-bytes

[c++] Difference between long and int data types

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