Pen and paper methodology

In the unit, we shall be doing a lot of work on computers, where your programs are auto-marked by the machine and instant feedback is given. However, one skill is critical for good understanding of programming and improving problem solving skills -

We will start with trace of some programs to establish what we expect students to do while tracing through code.

Tracing conditions

Trace the flow of the following program and determine the value of result at the end of it.

Solution

a < b is true

b % a == 0 is true

a % 2 == 0 is false

The expression becomes true && true && false

This is false

Hence, the else block executes and result becomes b (10).

Tracing conditions

Trace the flow of the following program and determine the value of result at the end of it.

Solution

a == b is false,

else executes

b decreases by 5, becomes 5 a == b is true. if block executes and result becomes b (5).

Tracing condition and loop

Trace the flow of the following program and determine the value of result at the end of it.

Solution

i	i<=7	i%2	i%2==1	result
1	true	1	true	-3+1 = -2
2	true	0	false
3	true	1	true	-2+3 = 1
4	true	0	false
5	true	1	true	1+5 = 6
6	true	0	false
7	true	1	true	6+7 = 13
8	false

Tracing nested conditions

Trace the flow of the following code -

Solution

At the end of the code, a = 5, b = 10, c = 2, d = false, result = 10. Explanation -