Using clrscr() without conio.h header file

[kristien]

hi friends,
I've a small doubt. can u help me? is it possible for clrscr() to work without conio header file.I found its working but i dono how its possible.If u've answer pls reply.

[r035198x]

You can define your own function called clrscr() and it would "work".

[kristien]

its not about defining our own functions for clrscr(). I jus found that clrscr function working without conio(header file). and i jus want to know is it possible? and how?

[r035198x]

It's not a standard function. You have to have included some header file where it was defined for it to work.

[Banfa]

Actually in C there is no requirement for a function to be declared before it is called if the required library is included in the link then there would be no need to include the header in the source.

Doing this is very very bad practice.

[vinayvaka]

yes it is true that clrscr() function will be in conio.h
but some times compiler will include this hedder file automatically, i have faced same situation 2years back.Still its our responsibility to include all hedder files where our function definitions are there.
so dont waste time on this things.

[arnaudk]

yes it is true that clrscr() function will be in conio.h
but some times compiler will include this hedder file automatically, i have faced same situation 2years back.Still its our responsibility to include all hedder files where our function definitions are there.
so dont waste time on this things.

Including the header file is not the issue. Read post #5 carefully. So long as the required library is linked then the code will work in principle, although this is a really sloppy way of doing things.
If you turn more compiler warnings, your compiler will probably warn you that you are using a function without declaring it which is bad practice.

Aside from this, it's possible that the conio.h header is included anyway by some other headers but don't take that for granted.

[kristien]

Thanks for ur replies.i found them really helpful.

[caochitam]

Step1: backup conio.h in "Include" folder of compiler.
Step2: Overwrite following code in to conio.h:

/*  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 */
 
extern   int _Cdecl directvideo;
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 */
 

Step3: Save conio.h and restart compiling.
Enjoy!
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