C166 User's Guide

Pointers with Memory Types

Memory types may used in pointer declarations to define the memory area of the object referenced or even the memory area where the pointer is located. In general, pointers should be declared according to the following rules:

Variable Declaration	Pointer Size	Pointer Declaration
char c;	16/32-bit	char *ptr; (Pointer size depends on the memory model in use)
int near nc;	16-bit	int near *np;
float sdata nf;	16-bit	float sdata *sp; or float near *sp;
long bdata x;	16-bit	long bdata *xp; or long near *xp;
char idata index;	16-bit	char idata *ip; or char near *ip;
const char near n = 5;	16-bit	char near *cp; (const may be ignored)
unsigned long far l;	32-bit	long far *lp;
char huge hc;	32-bit	char huge *hc_ptr;
long xhuge xl;	32-bit	char xhuge *hl_ptr;
void near func1 (void);	16-bit	void (near *fp1) (void);
int far func2 (void);	32-bit	int (far *fp2) (void);

Note

• Pointers to sdata, idata, or bdata objects may so be declared with the near memory type because a near pointer can hold the DPP for all objects that have a logical 16-bit address.
• In the TINY model, the memory type for pointer declarations are unnecessary because each object is accessed via a 16-bit address.
• near objects can be addressed with a far, huge, or xhuge pointer. The far, huge, or xhuge pointer access always yields DPP load or EXTS/EXTP instructions.
• A near pointer access uses the pre-loaded DPP registers and cannot be used to address a far, huge, or xhuge object.

The following examples illustrate several different declaration types:

char near *px

char near *idata pdx

struct time { char hour; char min; char sec; struct time near *pxtime; }

struct time far *ptime

ptime->pxtime->hour = 12