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D.3.5

Construct code to implement assessment statements D.3.1–D.3.4.

Teaching Note:

Students may be asked to trace, explain or construct algorithms using the concepts associated with the terms.

Sample Questions - General Tracing Questions from the Former Curriculum, which could apply here, and the next few assessment statements:

Study the algorithm shown below and answer the questions that follow.

```public class Prog
{ public static void main(String args [])
{  new Prog();
}

public Prog()
{ String s = "xxx";
getData(s);
output("end");
}

void getData(String p)
{ String a, b;
a = inputString("Enter String");
while (!a.equals(p))
{ b = inputString("Enter String");
output(zing(a,b));
a = inputString("Enter String");
}
}

String zing(String a, String b)
{ if (a.length() > 6) return "*******";
else
{ int d = a.length();
for (int i=0; i<6-d; i++)
a = a + " ";
return (a+b);
}
}
}```

The following pairs of data are entered into the program. The first value is stored in
variable a and the second in variable b in method getData().

```Value stored in variable a         Value stored in variable b
abc                                defg
abcdef                             g
abcdefg                            h
ab                                 cedfg```
(a) Copy and complete the following trace table to show what is output at line
output(zing(a,b)); for each pair of inputs above.
```a=inputString();      |       b=inputString();       |      output
abc                   |       ____                   |      ____
____                  |       defg                   |      ____```

[3 marks]

(b) Explain why the trace does not reach the line output("end"); . [2 marks]

(From here on, it's more analysis of algorithms, rather than tracing of algorithms... might not apply here, but might, in the new curriculum.)

(c) Suggest a way to fix this problem. [1 mark] (refer to the sample question in 2.1.4, and accompanying questions (a) and (b)).

(e) Outline what method zing() does and suggest a practical use for the methodwhen outputting a table of data values. [2 marks]
(also refer to the sample question in 2.1.4, and accompanying questions (a) and (b)).

JSR Notes:

The best thing here is to look at lots of past papers.