Types of chart you need for the exam and a note on 2-D arrays for SL (??)

I wrote a post on the OCC Computer Science highlighting the discrepancy between the Guide and the specimen paper:

Syllabus point 4.2.4 Teacher’s Note:

“Students will not be expected to construct a flow chart to represent an algorithm in an externally assessed component.”

Specimen SL Paper 1, Question 7:

When the wages for company employees are calculated, all hours above 38 are paid at the overtime rate of 1.5 times the base rate. Construct a flowchart that represents this algorithm.

The reply eventually came back from the IB:

Question 7 in the standard level paper 1 Computer Science specimen paper was included in error as it contradicts the teacher’s note, 4.2.4, in the syllabus.  As per this note, students will not be expected to construct flow charts to represent algorithms in externally assessed components. The IB apologises for the inconsistency in the specimen paper; this will be revised at the earliest opportunity.  It should be noted that students may be asked to draw flow charts when being tested on 1.2.7 in the syllabus.

I also asked about syllabus point 1.2.7.:

Drawing system flowcharts was on the old syllabus, but I notice here there is a reference to DFDs. As I remember from college, a DFD is a very specific thing and drawing one requires quite a lot of expertise. To what extent can students be expected to construct a data flow diagrams in the exam? Does anyone actually teach DFDs in any depth?

The reply came from Dave Mulkey and is worth reading:

Item 1.2.7 specifically says “system flow charts, data flow diagrams, structure chart… UML is not required.”  Lacking specific examples, I am assuming that “system flow chart” has arrows and/or lines connecting modules, “data flow diagram” has arrows connecting modules plus data flow labelled on the arrows, “structure chart” is a top-down hierarchical breakdown of a problem.  The statement “UML is not required” indicates to me that the others are just generic concepts without any specific requirements.  So I don’t think students need to worry greatly about just exactly what is required for a DFD (except that DATA FLOW should be included).  But they SHOULD know that these are NOT algorithmic (programming) flowcharts.  If 1.2 is supposed to be taught in 10 hours altogether, this single assessment statement can’t require more than about an hour to teach, and at most an hour of practice by the students. 

He then points out another problem with the specimen paper and the Guide:

Standard Level Specimen Paper 1 #10 d – asks the students to describe how a two-dimensional array could be used.  However, it is clear to me that only LINEAR arrays are required for SL students, and the 2-D arrays are specifically added for HL students.  So this question is inappropriate for SL students. Be that as it may, I will now teach 2-D arrays to my SL students – briefly – just in case a similar question appears in a real exam.


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