READ (II)                    3/15/72                    READ (II)

NAME            read  --  read from file

SYNOPSIS        (file descriptor in r0)

                sys read; buffer; nbytes  / read = 3.

                (nread in r0)

DESCRIPTION     A file descriptor is a word returned from a suc-

                cessful open or creat call.

                Buffer is the location of nbytes contiguous bytes

                into which the input will be placed.  It is not

                guaranteed that all nbytes bytes will be read;

                for example if the file refers to a typewriter at

                most one line will be returned.  In any event the

                number of characters read is returned in r0.

                If r0 returns with value 0, then end-of-file has

                been reached.

SEE ALSO        open(II), creat(II)

DIAGNOSTICS     As mentioned, r0 is 0 on return when the end of

                the file has been reached.  If the read was

                otherwise unsuccessful the error bit (c-bit) is

                set.  Many conditions, can generate an error:

                physical I/O errors, bad buffer address, prepos-

                terous nbytes, file descriptor not that of an in-

                put file.

BUGS            --