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Comment by scott_s | Hacker News Reader

Typically on 32-bit:

  sizeof(char) == 1
  sizeof(short) == 2
  sizeof(int) == 4
  sizeof(long) == 4
  sizeof(long long) == 8
  sizeof(void* ) == 4

Typically on 64-bit:

  sizeof(char) == 1
  sizeof(short) == 2
  sizeof(int) == 4
  sizeof(long) == 8
  sizeof(long long) == 8
  sizeof(void* ) == 8

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You'll see this typically listed as a LP64 model. The other common option is ILP64, where int == long == long long == void * == 8.

It should also be noted that this has nothing to do with the underlying hardware. Instead it's a decision made by the OS ABI. There's nothing that says you can't have sizeof(int) == 8 on a 32-bit system.

Just to add: Windows x64 is LLP, int = 4, long = 4, long long = 8, void* = 8

While it has nothing to do with hardware per se, ILP64 is often seen on platforms, where some significant 32 bit operations (often memory accesses, but surprisingly sometimes even ALU ops) are (or used to be) slower than 64 bit.

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