1. The program handles arithmetic operations for real numbers, including positive and negative numbers:
- Real number
+,-,*,/Real number (positive or negative). - Positive
+,-,*,/Negative.
2. Supports calculations with large numbers, up to 30 digits.
3. The first and second input fields must not be empty or contain invalid characters.
- If violated, an error message appears when the field loses focus, prompting correction before proceeding.
4. When an input field gains focus, its entire content should be selected automatically to facilitate quick replacement.
5. Only one operation can be selected at a time.
6. After entering two valid numbers and selecting an operation:
- Pressing the "Calculate" button displays the result in a read-only field.
7. For division:
- If the divisor is
0, the program shows an error message and focuses on the second input field for correction.
8. Upon pressing the "Exit" button:
- A confirmation dialog asks if the user wants to quit.
- Exiting closes the program, while canceling returns to the program.