26 lines
795 B
C
26 lines
795 B
C
#ifndef GW_VIRMEM_H
|
|
#define GW_VIRMEM_H
|
|
|
|
#include <stdint.h>
|
|
|
|
/*
|
|
* Virtual 8086 address space for DEF SEG / PEEK / POKE.
|
|
*
|
|
* Real GW-BASIC runs in a 1MB address space where programs routinely
|
|
* peek and poke at the BIOS data area and CGA video buffer. We emulate
|
|
* just enough of that space to make classic tricks work:
|
|
*
|
|
* 0040:0000 BIOS data area (keyboard flags, timer ticks, cursor pos)
|
|
* B800:0000 CGA text video buffer (char/attr pairs, 80x25 = 4000 bytes)
|
|
*
|
|
* Everything else reads as 0 and writes are silently discarded.
|
|
*/
|
|
|
|
/* Read a byte from virtual memory at segment:offset */
|
|
uint8_t virmem_peek(uint16_t segment, uint16_t offset);
|
|
|
|
/* Write a byte to virtual memory at segment:offset */
|
|
void virmem_poke(uint16_t segment, uint16_t offset, uint8_t value);
|
|
|
|
#endif
|