← Years 9–10 Digital Systems

Data flow diagram of a system

A diagram that shows how data moves between users, processes, data stores and external services in a system, using labelled arrows for each flow.

Part of: 9-10 Digital Technologies Vic Curric - Digital Systems and Security — Module 73, VCE Software Development - U4O2 - Cyber Security: secure software development practices — Module 74

Understanding Data flow diagram of a system in Years 9–10 Digital Systems

What it does: The label on the arrow names the data moving along it, so anyone reading the diagram knows exactly what is sent. Saving data is shown as a flow from a process to a data store, with the arrow labelled with the data being stored. A data flow diagram focuses on where data travels in a system, not on the code that makes it work. A data store is where data is kept for later, like a database or file. The student is an external entity. Processes do something with data. Data stores only hold it. A fixed version is [Student] -- username --> (Check login) -- lookup --> =Accounts DB=. Processes handle the data, and labels say what is flowing.

Common mistakes: Data cannot flow straight from a data store to an entity. It must pass through a process. The line should be {Accounts} -> (Login): record. Every data flow arrow needs a label that names the data moving along it. This line should be (Save) -> {Files}: file data.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add Data flow diagram of a system to a class →

This module's key terms are also in a printable crossword (Modules 70–79) and word search (Modules 41–79).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning
Duo
What does a data flow diagram show?
How data moves between users, processes, storage and external servicesThe exact lines of code a program runs, in order
Matches
[Student] --> =Accounts DB=
↓
An entity is sending data straight into a data store with no process in between and no label on the arrow. Data should pass through a process, and the flow should be labelled.
Applying
Meanings
Term
data flow diagram
Meaning
A diagram that shows how data moves between users, processes, data stores and external services in a system, using labelled arrows for each flow.
Practice
[User] -> (Check Login) : username, password
Testing
Gaps
: Student
Check Answer
Spots
2(Login) -> {Accounts}: check
3{Accounts} -> [User]: record

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

The 'Armadillo' badge — Shield Bearer, one of Cloodit's 106 collectible badges
Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy
Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games
Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print
Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. What does a data flow diagram show?
A. How data moves between users, processes, storage and external services ✓
B. The exact lines of code a program runs, in order
A data flow diagram focuses on where data travels in a system, not on the code that makes it work.
2. Which one is an external entity in a login system?
A. The step that checks the password
B. The user who types in a username and password ✓
An entity is a person or outside system that sends or receives data. Checking the password is a process.
3. Which one is a data store in a data-saving system?
A. A student typing in a form
B. A user accounts database ✓
A data store is where data is kept for later, like a database or file. The student is an external entity.
4. Which label is best for an arrow from the user to the login process?
A. Username and password ✓
B. Data
Each arrow should name the specific data that flows. A vague label like 'Data' does not tell the reader anything.
5. What is a process in a data flow diagram?
A. A step that takes in data and changes it or makes a decision, like 'Check login' ✓
B. A place where data is stored permanently, like a database
Processes do something with data. Data stores only hold it.

Match the Pairs

[Student] --> (Check login) → An entity (the student) sends data into a process, shown as an arrow from the entity to the process
=Accounts DB= → A data store, which is where the system keeps data such as user accounts so it can be used later
Every arrow in a data flow diagram must be labelled with the data it carries → [Student] -- username + password --> (Check login)
A process that saves data sends it to a data store, and the arrow shows what is saved → (Save score) -- new score --> =Scores DB=
[Student] --> =Accounts DB= → An entity is sending data straight into a data store with no process in between and no label on the arrow. Data should pass through a process, and the flow should be labelled.
(Check login) -- login result -- [Student] → The flow has no arrowhead, so the direction of the data is unclear. Every data flow needs an arrow showing which way the data moves.

Key Term

data flow diagram
A diagram that shows how data moves between users, processes, data stores and external services in a system, using labelled arrows for each flow.

Fill in the Blanks

1. entity: Student process: Log in store: Accounts
Hint: Type the data flow diagram word for a person or outside party that sends or receives data.
2. entity: Student process: Log in store: Accounts
Hint: Type the word for a step that checks or changes data.
3. entity: Student process: Save score store: Scores
Hint: Type the word for the place where data is kept until it is needed.
4. Student -> Log in : login details Log in -> Accounts : look up user
Hint: Type the arrow symbol that shows the direction data flows.
5. Student -> Log in : login details Log in -> Accounts : look up user Accounts -> Log in : user record
Hint: Type the name of the data store that sends the record back to the process.

Spot the Error

Question 1
A [User] -> (Login): username
B (Login) -> {Accounts}: check
C {Accounts} -> [User]: record
D (Login) -> [User]: result
Line C — Data cannot flow straight from a data store to an entity. It must pass through a process. The line should be {Accounts} -> (Login): record.
Question 2
A [Student] -> (Save): file
B (Save) -> {Files}
C (Save) -> [Student]: receipt
Line B — Every data flow arrow needs a label that names the data moving along it. This line should be (Save) -> {Files}: file data.
Question 3
A [Shopper] -> (Order): details
B [Shopper] -> {Orders}: order
C (Order) -> [Shopper]: receipt
Line B — An entity cannot write straight into a data store. A process must handle the data first. The line should be (Order) -> {Orders}: save.
Question 4
A [Member] -> (Sign up): details
B (Sign up) -> {Members}: save
C (Sign up) -> [Mailer]: address
D [Mailer] -> [Member]: welcome
Line D — Data should not flow directly between two external entities, because the system is not involved. The welcome message should come from the (Sign up) process.
Question 5
A [Teacher] -> (Marks): grades
B (Marks) -> {Results}: save
C (Report) -> {Results}: marks
D (Report) -> [Teacher]: report
Line C — The arrow is the wrong way round. The report process needs to read marks from the store, so it should be {Results} -> (Report): marks.

Student with a class code? Join your class →