GETC(III)                    4/30/72                    GETC(III)


     getc, getw, fopen  -  buffered input


     mov     $filename,r0

     jsr     r5,fopen; iobuf

     fopen(filename, iobuf)

     char *filename;

     struct buf *iobuf;

     jsr     r5,getc; iobuf

     (character in r0)


     struct buf *iobuf;

     jsr     r5,getw; iobuf

     (word in r0)


     struct buf *iobuf;


     These routines provide a buffered input facility.  Iobuf  is

     the address of a 518(10) byte buffer area whose contents are

     maintained by these routines.  Its structure is

             struct buf {

                     int fildes;     /* File descriptor */

                     int nleft;      /* Chars left in buffer */

                     char *nextp;    /* Ptr to next character */

                     char buff[512]; /* The buffer */


     Fopen may be called initially to open the file.  On  return,

     the  error  bit (c-bit) is set if the open failed.  If fopen

     is never called, get will read from the standard input file.

     From C, the value is negative if the open failed.

     Getc returns the next byte from the file in r0.   The  error

     bit  is  set  on  end  of file or a read error.  From C, the

     character is returned as an integer, without sign extension;

     it is -1 on end-of-file or error.

     Getw returns the next word in r0.  Getc and getw may be used

     alternately; there are no odd/even problems.  Getw is may be

     called from C; -1 is returned on end-of-file or  error,  but

     of course is also a legitimate value.

     Iobuf must be provided by the user; it must  be  on  a  word


     To reuse the same buffer for another file, it is  sufficient

     to close the original file and call fopen again.


     open (II), read (II), getchar (III), putc (III)


     c-bit set on EOF or error; from C, negative return indicates

     error  or  EOF.  Moreover, errno is set by this routine just

     as it is for a system call (see introduction (II)).