Stream can be a logical stream name or a physical stream number.
Success: [eclipse]: open(file1,write,s), at(s, P1), > write(s, 1234567890), at(s, P2), close(s). P1 = 0 P2 = 10 yes. [eclipse]: open(file1,update,s), at(s, P1), read(s, T), > at(s, P2), close(s). P1 = 0 T = 1234567890 P2 = 10 yes. Error: at(Stream, 4). (Error 4). at("3", Pointer). (Error 5). at(7, 4.3). (Error 5).