Ep 4: Major site identifiers suggestion

[ajerrison-manchester]

In Episode 4 "Calculating New values" the exercise "Major Site Identifiers" could be improved by a brief example of what substr() and instr() do as there has been no previous mention of them. I realise the instructor can demo this, but it appears to be an exercise for those who have finished quickly, i.e. something for them to do while the instructor helps other students. Ideally there should be an example the instructor can leave on screen while he/she is going round the room helping others.