A third type of pointer in Microsoft C/C++ is the “huge” pointer, which applies only to data pointers. Code pointers cannot be declared as huge.
A huge address is similar to a far address in that both contain 32 bits, made up of a segment value and an offset value. They differ only in the way pointer arithmetic is performed.
For far pointers, Microsoft C/C++ assumes that code and data objects lie completely within the segment in which they start, so pointer arithmetic operates only on the offset portion of the address. Limiting the size of any single item to 64K makes pointer arithmetic faster.
Huge pointers overcome this size limitation; pointer arithmetic is performed on all 32 bits of the data item's address, thus allowing data items referenced by huge pointers to span more than one segment.
In this code fragment,
int __huge *hp;
int __far *fp;
.
.
.
hp++;
fp++;
both hp and fp are incremented. The huge pointer is incremented as a 32-bit value that represents the combined segment and offset. Only the offset part of the far pointer (a 16-bit value) is incremented.
Extending the size of pointer arithmetic from 16 to 32 bits causes such arithmetic to execute more slowly. You gain the use of larger arrays by paying a price in execution speed.