4.1.1.10 Subroutines Quiz: AQA Computer Science, Unit 1

The 20 questions

1. What is a subroutine?

   • A data type built from records that groups several fields together under one shared name
   • A named block of code that is called by writing its name
   • A variable that stores a memory address pointing to a block of code held elsewhere in memory
   • A loop that runs a fixed number of times, with its counter updated at the end of each pass

2. Which is an advantage of using subroutines in a program?

   • The same code can be reused without being written out again
   • Variables no longer need declaring
   • The program always uses less memory than any alternative
   • Errors are removed automatically

3. What is the difference between a procedure and a function, as commonly defined?

   • A function returns a value to the caller, while a procedure does not return a value
   • Procedures and functions are identical in all respects
   • A function can only be called from within itself
   • A procedure returns a value, while a function never returns anything

4. A program has a subroutine called printHeader that is used at the start of several outputs. Why is this a sensible design?

   • It makes the header appear in every line of the program, so that every output line is formatted
   • It forces the program to run more slowly, but the code is easier to read for other programmers
   • It stops the program needing any variables, because the subroutine stores all the values it needs
   • It avoids repeating the same code and so reduces errors when changing it

5. A subroutine is called from several places in a program. Where is the code of the subroutine stored?

   • Once for each place it is called, so the code is copied to each place that uses the subroutine
   • In the main program only, and the subroutine itself is kept in a separate file on disk each time
   • In a constant named after the subroutine, so that the code cannot be changed during execution
   • Once, in a single place, and each call transfers control to it

6. A program calls a subroutine from line 20 and the subroutine finishes. Where does control normally return?

   • To line 1 of the subroutine
   • To the start of the program
   • To the end of the file where the program stops immediately
   • To the statement after the call on line 20

7. Which statement best describes a subroutine's role in structured design?

   • It is a named, self-contained task that can be reused and tested separately
   • It is a loop that must run before the main program, setting up the values used by the main program
   • It is a type of file on disk that holds the output of the program in a fixed binary layout
   • It is a constant used to store results that the main program reads in at the end of the run

8. Why are subroutines sometimes described as out-of-line blocks of code?

   • Because they are only used in printing
   • Because they are always written at the end of the file and never run
   • Because they are stored apart from the main sequence and entered only when called
   • Because they cannot contain any statements

9. A subroutine named total is called 3 times in a program, and each call returns a value used in a sum. What does this show?

   • The subroutine can only be called once, because a second call would overwrite its stored result
   • Each call must use a different subroutine name, because a name can only be called once in a program
   • The sum must be stored as a constant, since a variable would change each time the subroutine runs
   • The same subroutine can be reused to produce several results

10. Which statement about the advantages of subroutines is most accurate?

    • They remove the need for variables and loops everywhere, because all work is done by calls
    • They make all data global by default, so every subroutine can read and write every value
    • They help to decompose a problem, making it easier to design, read and test
    • They guarantee that no errors will ever occur, so testing of each subroutine is not needed

11. A programmer writes a subroutine to calculate VAT and calls it in two different parts of a shop program. What is the main benefit?

    • The VAT calculation runs twice as fast, because the subroutine is compiled separately from the program
    • The calculation becomes a Boolean, so the program records only whether VAT applies to each sale
    • The program no longer needs a VAT rate, since the subroutine works out the rate from the price
    • The VAT calculation is defined once, so a change to the rate is made in one place

12. A subroutine is defined but never called in the main program. What is its effect?

    • It causes the program to crash
    • It changes every variable in the program
    • It is never executed while the program runs
    • It runs automatically at the start of the program

13. A program uses a subroutine to check a password, and the check is needed at both sign in and sign up. What is the best reason to write it as a subroutine?

    • So that the password is stored in a constant, which means the value can never be changed later
    • So that no selection is needed in the program, because the check replaces every IF statement
    • So the check always returns TRUE, so that any password entered is accepted without an error
    • So the same checking logic is used in both places without duplication

14. Which term describes a subroutine that is defined inside another subroutine or program and only used there?

    • Nested subroutine
    • Global constant
    • Record field
    • Pointer variable

15. A program needs to run a sequence of instructions for a menu option, then return to the menu. What is the most natural use of a subroutine?

    • Store the instructions in a constant string, which the program then reads one character at a time
    • Copy the instructions into every menu option, so that each option carries its own full sequence
    • Use a Boolean to show the menu, so that the menu options are selected by a yes-or-no question
    • Wrap the sequence in a named subroutine and call it from the menu

16. Which statement about naming a subroutine is most accurate?

    • The name must be a single letter for speed, since the compiler looks up short names faster
    • A good name describes what the subroutine does so its call reads clearly
    • The name must always be the same as a variable, so that the call and the variable share memory
    • The name has no effect on how the program is read, because the compiler ignores the identifier

17. A subroutine call appears inside a loop that runs 100 times. How many times is the subroutine executed?

    • 100
    • 10
    • 0
    • 1

18. Why are subroutines useful when a program is being tested?

    • Each subroutine can be tested separately with known inputs and expected outputs
    • They replace the need for any input data, so the test can be run without supplying values
    • They prevent tests from being written at all, because subroutines cannot be checked separately
    • They remove all bugs from the main program automatically, so the program needs no later testing

19. A program calls a subroutine that itself calls a second subroutine. What is needed so the program can resume correctly after the second subroutine finishes?

    • All variables must be deleted
    • The second subroutine must be a constant
    • The program must restart from the beginning
    • The return address for each call must be remembered

20. A subroutine is used to print a line of stars 20 characters long. Which is a sensible design choice for its length?

    • Pass the length as a parameter so the subroutine can print any length
    • Hardcode 20 and also store it as a global variable and a constant
    • Change the length in every call by copying the code
    • Make the length a Boolean

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