2. Context level (0) DFD to model the programming of a VCR TV guide Tape retailer VCR program VCR Visual program data New tape VCR program data tape VCR status data

3. A level 1 DFD to model the programming of a VCR read data TV guide get tape tapes at home Tape retailer put tape VCR resolve error enter VCR data monitor VCR handle tape error visual program data VCR data New tape home tape done-with tape VCR program data tape selected tape VCR status data decide on tape extract /insert control VCR status tape directive data entry control

4. DSD for control flow “VCR status” VCR status Display panel data Tape status Programming status Tape ejectedTape accepted oo Program OK o No program o “no-tape” LED on “tape-in” LED on “prog-present” LED on “prog-present” LED off Boolean

5. DSD for control flow “tape directive” tape directive Deductive thought Get tape from VCR Put tape in VCR oo Boolean

6. FSM for control process “extract/insert control” Idle Extracting Inserting Tape ejected Get tape from VCR Tape accepted Program OK Put tape in VCR Tape accepted

7. SC for data process “read data” read data Locate valid TV guide Choose programme Read program details Scan rooms Check guides for date Locate right page in guide Scan for right program Confirm data format Memorise data