Update pack.md

Author: walbourn

docs/preprocessor/pack.md

@@ -37,7 +37,7 @@ The statement `#pragma pack (pop, r1, 2)` is equivalent to `#pragma pack (pop, r
 
 ## Remarks
 
-To *pack* a class is to place its members directly after each other in memory. It can mean that some or all members can be aligned on a boundary smaller than the default alignment of the target architecture. **pack** gives control at the data-declaration level. It differs from compiler option [/Zp](../build/reference/zp-struct-member-alignment.md), which only provides module-level control. **pack** takes effect at the first **struct**, **union**, or **class** declaration after the pragma is seen. **pack** has no effect on definitions. Calling **pack** with no arguments sets *n* to the value set in the compiler option `/Zp`. If the compiler option isn't set, the default value is 8.
+To *pack* a class is to place its members directly after each other in memory. It can mean that some or all members can be aligned on a boundary smaller than the default alignment of the target architecture. **pack** gives control at the data-declaration level. It differs from compiler option [/Zp](../build/reference/zp-struct-member-alignment.md), which only provides module-level control. **pack** takes effect at the first **struct**, **union**, or **class** declaration after the pragma is seen. **pack** has no effect on definitions. Calling **pack** with no arguments sets *n* to the value set in the compiler option `/Zp`. If the compiler option isn't set, the default value is 8 for x86, ARM, and ARM64. The default is 16 for x64 native.
 
 If you change the alignment of a structure, it may not use as much space in memory, but you may see a decrease in performance or even get a hardware-generated exception for unaligned access.  You can modify this exception behavior by using [SetErrorMode](/windows/win32/api/errhandlingapi/nf-errhandlingapi-seterrormode).