$ cat hands-on/number-menu.spec HO-12

Area 06 · Control structures

Number tools menu

A menu-driven program that runs small number tools until the user exits, the classic shape of a hands-on console program.

Spec no.: HO-12
Level: Exam-level
Time box: 1 h 15 min
Reference: Java · C#
Grading: Self-assessed · rubric is ours, not DICT's

01 Coverage

Area	Sub-skills practised	Role
01 Data manipulation	Validation	Also
06 Control structures	Conditional, Iteration	Primary

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Read the task freely. An account is required before editing and running a solution. Code runs also need an internet connection.

02 Requirements

Each line is a choice and a value: 1 n prime check, 2 n digit sum and reverse, 3 n multiplication table (n from 1 to 12, ten rows), 4 n centred pyramid of n rows (1 to 20).
0 prints Bye and ends the program; ignore anything after it.
Any unknown choice, missing value, non-number or out-of-range value prints Invalid choice.
Prime check must stop at the square root.
Digit sum and reverse must use % and /, not string reversal.
The pyramid uses nested loops: row r has n − r spaces and 2r − 1 stars.

03 Input and output

Input

Lines of choice value
0 to exit

Output

29 is prime / 91 is not prime
Digit sum s, reversed r
Table rows n x i = p
Pyramid rows
Invalid choice / Bye

Sample input · stdin

Expected output · stdout

29 is prime
91 is not prime
Digit sum 7, reversed 4021
  *
 ***
*****
Invalid choice
Invalid choice
Bye

Match the sample exactly first, then write at least two test inputs of your own.

04 Edge cases to test

1 0 and 1 1 (not prime)
2 1200 (reverse is 21)
3 13
4 abc

05 Starter outline and hints

Outline

loop over lines
switch(choice): 0 → Bye, return; 1..4 → validate value → run tool
default → Invalid choice

Hints

Hint 1

In Java a labelled break leaves the loop from inside a switch; in C# a return or a flag does the same.

06 Practice rubric

Criterion	Sub-skills	Look for	Pts
Menu control	ConditionalIteration	One loop, one dispatch, exit on 0, every bad input caught.	30
Prime and digits	Iteration	Square-root bound; arithmetic digit handling.	30
Nested loops	Iteration	Pyramid and table shapes exactly as specified.	25
Validation	Validation	Range checks per option.	15
Total			100

Our own weighting for practice. It is not the DICT scoring scheme.

07 Self-check

Tick only what you have verified by running your own program.

91 is reported as not prime (7 × 13).
The program stops reading after 0.
My pyramid has no trailing spaces.
I can explain why checking up to √n is enough.

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08 Reference solution

Both versions compiled and reproduced the sample output on Java 21 and .NET 8 when this site was built. Reference solutions are in Java and C#. The 2023 FAQ copy also lists C, C++ and Visual Basic 6.0 / .NET; the same structure carries over, but you will need your language's own file and database APIs.

Try the whole brief first. The reference is one correct approach, not the only one, and reading it early removes most of the practice value.

09 Exam-day habits

Work without internet search to simulate exam conditions.
Type the sample input yourself and compare your output line by line before you look at the reference.

Area

Sub-skills practised

Role

01 Data manipulation

Validation

Also

06 Control structures

Conditional, Iteration

Primary

02 Requirements

Each line is a choice and a value: 1 n prime check, 2 n digit sum and reverse, 3 n multiplication table (n from 1 to 12, ten rows), 4 n centred pyramid of n rows (1 to 20).

0 prints Bye and ends the program; ignore anything after it.

Any unknown choice, missing value, non-number or out-of-range value prints Invalid choice.

Prime check must stop at the square root.

Digit sum and reverse must use % and /, not string reversal.

The pyramid uses nested loops: row r has n − r spaces and 2r − 1 stars.