Borland C++ 3.1 for DOS 中directvideo的问题

      directvideo是控制DOS是否直接操纵视频缓冲区的开关，在conio.h中声明，而只有在 DOS环境下才会起作用。而在Borland C++ for window 下是没有作用的。主要在古老的DOS开发中经常的会使用的，这几天在搞Borland C++ for DOS 开发手持设备中，用到感觉有点迷惑了，记录下来，以防备忘.

   在Borland C++(包括Turbo C)中，缺省为直接操纵视频缓冲区，这在HT系列掌上电脑上和仿真环境中会引起死机现象，必须在主程序开始时加上“directvideo=0；”来抑制直接写屏操作.

 

/* conio.h

    Direct MSDOS console input/output.

    Copyright (c) 1987, 1992 by Borland International
    All Rights Reserved.
*/

#if !defined(__CONIO_H)
#define __CONIO_H

#if !defined(___DEFS_H)
#include <_defs.h>
#endif

#if !defined(_Windows)

#define _NOCURSOR 0
#define _SOLIDCURSOR 1
#define _NORMALCURSOR 2

struct text_info {
    unsigned char winleft;
    unsigned char wintop;
    unsigned char winright;
    unsigned char winbottom;
    unsigned char attribute;
    unsigned char normattr;
    unsigned char currmode;
    unsigned char screenheight;
    unsigned char screenwidth;
    unsigned char curx;
    unsigned char cury;
};

enum text_modes { LASTMODE=-1, BW40=0, C40, BW80, C80, MONO=7, C4350=64 };

#if !defined(__COLORS)
#define __COLORS

enum COLORS {
    BLACK, /* dark colors */
    BLUE,
    GREEN,
    CYAN,
    RED,
    MAGENTA,
    BROWN,
    LIGHTGRAY,
    DARKGRAY, /* light colors */
    LIGHTBLUE,
    LIGHTGREEN,
    LIGHTCYAN,
    LIGHTRED,
    LIGHTMAGENTA,
    YELLOW,
    WHITE
};
#endif

#define BLINK 128 /* blink bit */
/*_cdecl 是C Declaration的缩写，表示C语言默认的函数调用方法：所有参数从右到左依次入栈，这些参数由调用者清除，称为手动清栈。被调用函数不需要求调用者传递多少参数，调用者传递过多或者过少的参数，甚至完全不同的参数都不会产生编译阶段的错误 　C中不加说明默认函数为_cdecl调用方式 */
extern int _Cdecl directvideo; //这里定义了directvideo 其实值只能是0或1而已
extern int _Cdecl _wscroll;

#endif /* !_Windows */

#ifdef __cplusplus
extern "C" {
#endif

void _Cdecl clreol( void );
void _Cdecl clrscr( void );
void _Cdecl gotoxy( int __x, int __y );
int _Cdecl wherex( void );
int _Cdecl wherey( void );
int _Cdecl getch( void );
int _Cdecl getche( void );
int _Cdecl kbhit( void );
int _Cdecl putch( int __c );

#ifndef _PORT_DEFS
unsigned char _Cdecl inportb( unsigned __portid );
unsigned _Cdecl inport ( unsigned __portid );
int _Cdecl inp( unsigned __portid );
unsigned _Cdecl inpw( unsigned __portid );
void _Cdecl outportb( unsigned __portid, unsigned char __value );
void _Cdecl outport ( unsigned __portid, unsigned __value );
int _Cdecl outp( unsigned __portid, int __value );
unsigned _Cdecl outpw( unsigned __portid, unsigned __value );
#endif /* !_PORT_DEFS */

#if !defined(_Windows)

void _Cdecl delline( void );
int _Cdecl gettext( int __left, int __top,
                            int __right, int __bottom,
                            void *__destin);
void _Cdecl gettextinfo (struct text_info *__r );
void _Cdecl highvideo( void );
void _Cdecl insline( void );
void _Cdecl lowvideo( void );
int _Cdecl movetext( int __left, int __top,
                             int __right, int __bottom,
                             int __destleft, int __desttop );
void _Cdecl normvideo( void );
int _Cdecl puttext( int __left, int __top,
                            int __right, int __bottom,
                            void *__source );
void _Cdecl textattr( int __newattr );
void _Cdecl textbackground( int __newcolor );
void _Cdecl textcolor( int __newcolor );
void _Cdecl textmode( int __newmode );
void _Cdecl window( int __left, int __top, int __right, int __bottom);

void _Cdecl _setcursortype( int __cur_t );
char * _Cdecl cgets( char *__str );
int _Cdecl cprintf( const char *__format, ... );
int _Cdecl cputs( const char *__str );
int _Cdecl cscanf( const char *__format, ... );
char * _Cdecl getpass( const char *__prompt );
int _Cdecl ungetch( int __ch );

#endif /* !_Windows */

#ifndef _PORT_DEFS
#define _PORT_DEFS

    /* These are in-line functions. These prototypes just clean up
       some syntax checks and code generation.
     */
unsigned char _Cdecl __inportb__ (unsigned __portid);
unsigned _Cdecl __inportw__ (unsigned __portid);
unsigned char _Cdecl __outportb__(unsigned __portid, unsigned char __value);
unsigned _Cdecl __outportw__(unsigned __portid, unsigned __value);

#define inportb(__portid) __inportb__(__portid)
#define outportb(__portid, __value) ((void) __outportb__(__portid, __value))
#define inport(__portid) __inportw__(__portid)
#define outport(__portid, __value) ((void) __outportw__(__portid, __value))

/* MSC-compatible macros for port I/O */
#define inp(__portid) __inportb__ (__portid)
#define outp(__portid, __value) __outportb__(__portid, (unsigned char)__value)
#define inpw(__portid) __inportw__ (__portid)
#define outpw(__portid, __value) __outportw__(__portid, __value)

#endif /* _PORT_DEFS */

#ifdef __cplusplus
}
#endif


#endif /* __CONIO_H */