求getcwd函数源码
不需要全路径，只需要获得当前运行程序的目录名就行，
想看一下源码怎么实现的，system调用？
[解决办法]
引用赵老师的话“单步调试和设断点调试是程序员必须掌握的技能之一。”

打断点，跟进去。windows下就是，主要就是调用GetFullPathName这个api
[解决办法]
先
http://www.microsoft.com/visualstudio/chs/downloads#d-2010-express
点开Visual C++ 2010 Express下面的语言选‘简体中文’，再点立即安装

再参考C:\Program Files\Microsoft Visual Studio 10.0\VC\crt\src\getcwd.c

...
/***
*_TSCHAR *_getdcwd(drive, pnbuf, maxlen) - get c.w.d. for given drive
*
*Purpose:
*       _getdcwd gets the current working directory for the user,
*       placing it in the buffer pointed to by pnbuf.  It returns
*       the length of the string put in the buffer.  If the length
*       of the string exceeds the length of the buffer, maxlen,
*       then NULL is returned.  If pnbuf = NULL, maxlen is ignored,
*       and a buffer is automatically allocated using malloc() --
*       a pointer to which is returned by _getdcwd().
*
*       side effects: no global data is used or affected
*
*Entry:
*       int drive   - number of the drive being inquired about
*                     0 = default, 1 = 'a:', 2 = 'b:', etc.
*       _TSCHAR *pnbuf - pointer to a buffer maintained by the user;
*       int maxlen  - length of the buffer pointed to by pnbuf;
*
*Exit:
*       Returns pointer to the buffer containing the c.w.d. name
*       (same as pnbuf if non-NULL; otherwise, malloc is
*       used to allocate a buffer)
*
*Exceptions:
*
*******************************************************************************/

_TSCHAR * __cdecl _tgetdcwd (
        int drive,
        _TSCHAR *pnbuf,
        int maxlen
        )
{
    _TSCHAR *retval;

    _mlock( _ENV_LOCK );
    __try {
        retval = _tgetdcwd_nolock(drive, pnbuf, maxlen);
    }
    _finally {
        _munlock( _ENV_LOCK );
    } 
 

    return retval;
}

#ifdef _DEBUG

_TSCHAR * __cdecl _tgetdcwd_dbg (
        int drive,
        _TSCHAR *pnbuf,
        int maxlen,
        int nBlockUse,
        const char * szFileName,
        int nLine
        )
{
    _TSCHAR *retval;

    _mlock( _ENV_LOCK );
    __try {
        retval = _tgetdcwd_lk_dbg(drive, pnbuf, maxlen, nBlockUse, szFileName, nLine);
    }
    _finally {
        _munlock( _ENV_LOCK );
    }

    return retval;
}

#endif  /* _DEBUG */

#ifdef _DEBUG

_TSCHAR * __cdecl _tgetdcwd_nolock (
        int drive,
        _TSCHAR *pnbuf,
        int maxlen
        )
{
    return _tgetdcwd_lk_dbg(drive, pnbuf, maxlen, _NORMAL_BLOCK, NULL, 0);
}

_TSCHAR * __cdecl _tgetdcwd_lk_dbg (
        int drive,
        _TSCHAR *pnbuf,
        int maxlen,
        int nBlockUse,
        const char * szFileName,
        int nLine
        )

#else  /* _DEBUG */

_TSCHAR * __cdecl _tgetdcwd_nolock (
        int drive,
        _TSCHAR *pnbuf,
        int maxlen
        )

#endif  /* _DEBUG */
{
    _TSCHAR *p;
    _TSCHAR drvstr[4];
    int ret, count;
    _TSCHAR *pname; /* only used as argument to GetFullPathName */

    if ( drive != 0 ) {
        /*
         * Not the default drive - make sure it's valid.
         */
        if ( !_validdrive(drive) ) {
            _doserrno = ERROR_INVALID_DRIVE;
            _VALIDATE_RETURN(("Invalid Drive",0), EACCES, NULL);
        }
    } else {
        /* Get the drive index of the default drive */ 
 
        drive = _getdrive();

    }

    /* If pnbuf is NULL, we pass 0 in both the 2nd & 3rd parameter
    to find required length to allocate */

    if(pnbuf)
    {
        _VALIDATE_RETURN( (maxlen > 0), EINVAL, NULL);
        count = maxlen;
        pnbuf[0] = 0;
    }
    else
        count = 0;

    /*
     * Get the current directory string on that drive and its length
     */
    if(drive!=0)
    {
        drvstr[0] = _T('A') - 1 + drive;
        drvstr[1] = _T(':');
        drvstr[2] = _T('.');
        drvstr[3] = _T('\0');
    }
    else
    {
        drvstr[0] = _T('.');
        drvstr[1] = _T('\0');
    }

    ret = GetFullPathName( drvstr, count, pnbuf, &pname );

    if(ret == 0) {
        _dosmaperr( GetLastError() );
        return NULL;
    }

    if( pnbuf != NULL ) {
        if(ret < count) {
            /* GetFullPathName always returns a value less than that
            passed in if successful i.e. we got the required dir */
            return pnbuf;
        }

        errno = ERANGE;
        *pnbuf = 0;
        return NULL;
    }

    /* The code comes here only if pnbuf was NULL
    Allocate the required memory & call GetFullPathName again*/

    maxlen = __max(ret, maxlen) ;
#ifdef _DEBUG
    if( (p = (_TSCHAR *)_calloc_dbg( maxlen, sizeof(_TSCHAR), nBlockUse, szFileName, nLine)) == NULL) {
#else  /* _DEBUG */
    if( (p = (_TSCHAR *)calloc( maxlen, sizeof(_TSCHAR))) == NULL) {
#endif  /* _DEBUG */
        errno = ENOMEM; 
 
        _doserrno = E_nomem;
        return NULL;
    }


    ret = GetFullPathName( drvstr, maxlen, p, &pname );

    if(ret == 0 
[解决办法]
 ret >= maxlen) {
        _dosmaperr( GetLastError() );
        return NULL;
    }

    return p;

}
...