Self-Assessment Quiz: Modules

Twenty questions to confirm you can build, expose, split, and compile modules before you move on to derived types. Aim for 16 or more. Answers and a topic map are at the end — try the whole quiz first.

Question 1

A module is best described as: - A. A program that runs on its own - B. A container for shared constants, variables, types, and procedures that other units access with use - C. A single procedure that can be called from anywhere - D. A file of preprocessor macros

Question 2

What does use kinds, only: dp do that a bare use kinds does not? - A. It makes the import faster at run time - B. It imports only dp, documenting the dependency and avoiding name clashes with other imports - C. It makes dp private - D. Nothing; the only: clause is decorative

Question 3

A module procedure is: - A. Any subroutine in any file - B. A subroutine or function defined after a module's contains statement - C. A procedure declared with COMMON - D. A procedure that must be pure

Question 4

A bare private statement (no list) at the top of a module: - A. Makes the module uncompilable - B. Hides every entity by default, so only those you explicitly mark public are visible outside - C. Makes every entity public - D. Applies only to variables, not procedures

Question 5

"An explicit interface for free" means that, because a procedure is in a module: - A. It runs faster - B. The compiler knows its full signature at every call site and checks calls against it - C. It never needs arguments - D. It is automatically parallel

Question 6

Which Chapter 6 feature does not require an explicit interface to work across files? - A. Keyword arguments - B. Optional arguments - C. Assumed-shape array arguments - D. A subroutine with only fixed-size scalar arguments passed positionally

Question 7

A private module variable can be changed from outside the module by: - A. Assigning to it directly - B. Only through the module's public procedures - C. An INCLUDE statement - D. Any program that uses the module

Question 8

Module variables are implicitly: - A. allocatable - B. save (they persist for the whole run and keep their value between calls) - C. pointer - D. re-initialized on every procedure entry

Question 9

A submodule exists to: - A. Be used directly by programs - B. Hold the bodies of separate module procedures whose interfaces are declared in the parent module - C. Replace the main program - D. Store data only

Question 10

Which prefix marks an interface body in a module as a separate module procedure (body in a submodule)? - A. external - B. pure - C. module (e.g., module function ...) - D. recursive

Question 11

The main practical benefit of submodules is: - A. Faster generated code at run time - B. Faster builds — editing a submodule body does not force recompilation of the parent module's users - C. Smaller executables - D. Automatic parallelism

Question 12

Inside a submodule, entities of the parent module (like a kind dp) are available: - A. Only after a use of the parent - B. By host association, with no use needed - C. Never - D. Only if declared public

Question 13

The modern replacement for a FORTRAN 77 COMMON block is: - A. An EQUIVALENCE statement - B. A module (with the shared state kept private and reached through procedures) - C. A GOTO - D. A pointer

Question 14

Why is a COMMON block dangerous compared to a module? - A. It is slower - B. Different routines can declare the same shared memory with different names, types, or lengths, and nothing checks the mismatch - C. It cannot hold real numbers - D. It requires a submodule

Question 15

A .mod file contains: - A. The compiled machine code of the module's procedures - B. The module's public interface (names, types, signatures) that a user needs at compile time - C. The program's output - D. The linker script

Question 16

The machine code for a module's procedures lives in: - A. The .mod file - B. The object (.o) file, which must still be linked - C. The source file only - D. Nowhere; modules are interpreted

Question 17

Fatal Error: Cannot open module file 'kinds.mod' almost always means: - A. The module source has a syntax error - B. kinds was not compiled before the file that uses it (wrong compile order or missing -I) - C. The module is too large - D. You must rewrite kinds as a submodule

Question 18

A circular module dependency (a uses b, b uses a): - A. Compiles but runs slowly - B. Cannot compile, because neither module can be compiled first - C. Is required for mutual recursion - D. Is fixed by adding implicit none

Question 19

For the heat-solver hierarchy (kinds; heat_solver and heat_io use kinds; heat uses all three), a valid compile order is: - A. heat, heat_io, heat_solver, kinds - B. kinds, heat_solver, heat_io, heat - C. heat_solver, kinds, heat, heat_io - D. Any order works

Question 20

"Private by default, public on purpose" is recommended because: - A. It compiles faster - B. Helpers you add later stay hidden automatically, so you can only leak an internal by explicitly publishing it - C. It is required by the standard - D. It makes all variables constant

Answer Key

Q Ans Why
1 B A module packages shared definitions for use; it is not a runnable program.
2 B only: imports named entities, documenting the dependency and avoiding clashes.
3 B A module procedure is defined after the module's contains.
4 B Bare private sets the default to hidden; expose with public ::.
5 B The module gives callers the full signature, so the compiler checks each call.
6 D Positional fixed scalars work with an implicit interface; the others need an explicit one.
7 B A private name is invisible outside; only the module's procedures can change it.
8 B Module variables have the save attribute implicitly and persist for the run.
9 B A submodule supplies bodies for the parent's separate module procedures.
10 C The module prefix marks a separate module procedure.
11 B Submodules cut rebuild cascades; run-time code is unchanged.
12 B A submodule sees its parent by host association.
13 B Modules replaced COMMON, ideally with private state behind procedures.
14 B COMMON overlays memory with no cross-routine type/length checking.
15 B A .mod holds the interface, read by users at compile time.
16 B The code is in the .o; the .mod is only the interface.
17 B The .mod does not exist yet — a compile-order (or -I) problem.
18 B Neither can be compiled first, so the cycle is rejected.
19 B kinds first (uses nothing), heat last (uses all).
20 B New helpers stay private unless you deliberately publish them.

Topics to review by question

  • Q1–3 → §8.1 (module, use, module procedures).
  • Q4–8, 20 → §8.2 (public/private, explicit interfaces, module variables).
  • Q9–12 → §8.3 (submodules).
  • Q13–14 → §8.4 (why modules replaced COMMON/INCLUDE).
  • Q15–19 → §8.5 (.mod files and compile order) and §8.6 (the hierarchy).

Scored below 16? Reread the flagged sections — modules underpin every chapter from here to the capstone, so this is the wrong place to have gaps.