Control flow analysis is a technique used to examine the sequence in which instructions or statements are executed within a program. In the given pseudocode, the key aspects to consider are the logical flow and any conditional branches that may lead to unreachable code.
The pseudocode provided is:
Program tax check
BEGIN
yearly := 0
tax := 0
get (monthly)
get (tax_rate)
for I = 1..12 loop
yearly := yearly + monthly
tax := tax - (tax_rate * monthly)
ENDLOOP
salary := monthly * 12
IF salary = yearly THEN
print ('Salary OK')
ELSE
print ('Salary not OK')
ENDIF
year_tax := salary * tax_rate
IF year_tax = tax THEN
print ('Tax Problem')
ENDIF
END tax check
Analysis:
Initialization and Input:
yearly and tax are initialized to 0. The program takes monthly and tax_rate as input.
Loop Execution:
The loop runs from 1 to 12, accumulating monthly into yearly and adjusting tax accordingly.
Salary Calculation and Check:
After the loop, salary is calculated as monthly * 12. The program then checks if salary is equal to yearly. Given the loop accumulates monthly into yearly 12 times, salary will always equal yearly, making the IF salary = yearly condition always true. Thus, the 'Salary OK' message will always be printed, and the ELSE branch will never be executed.
Yearly Tax Calculation and Check:
year_tax is calculated as salary * tax_rate. Then, it checks if year_tax is equal to tax. However, due to the accumulation and subtraction inside the loop, tax would likely not equal year_tax, making the condition IF year_tax = tax false in most practical scenarios. Therefore, the 'Tax Problem' message at line 19 is unlikely to be printed.
Conclusion:
Given this flow, the ELSE block associated with the IF salary = yearly condition (line 15) is unreachable. However, the critical analysis indicates that the code at line 19, which prints 'Tax Problem', is also unreachable due to the logic flow where the condition is rarely true.
Thus, the result is that line 19 is more certainly unreachable.
Reference:
This analysis is derived from standard control flow analysis principles covered in the ISTQB CTAL-TTA syllabus and sample questions . The conclusion aligns with the answers provided in the ISTQB sample exam answers document .
