- **Process** — the steps or calculations performed on those inputs: in general terms, *how* the input becomes the output.

- **Output** — the data the process produces. Also read off your DFD.

>| **Input** — data entering the process.

2. Compare the entered password with the stored password and set a valid/invalid flag.

>| **Process** — a step performed on the input.

3. An "Access granted" or "Access denied" message on the screen.

>| **Output** — the result the process produces.

Your data flow diagram already did the hard part. **Each process in the DFD becomes its own IPO chart:**

- the **arrows flowing in** → the Input column

- the **process** itself → the Process column (the steps)

- the **arrows flowing out** → the Output column

**🎯 Watch for:** how a single process from a DFD is turned into one IPO chart, with the data flows becoming the Input and Output rows.

{{Video|src=https://www.youtube.com/watch?v=YMOP0GlWXOY}}

Here is a DFD for a simple login system:


Each process in that diagram becomes one IPO chart. Start with the general shape:

| :--- | :--- | :--- |

| List the inputs as per the DFD | Explain, in general terms, how the processing/calculations convert the input to the output | List the outputs as per the DFD |

| Input | Process | Output |

| :--- | :--- | :--- |

| Two separate strings keyed in by the user. | Prompt the user for their username, then store the response in the `UserName` variable.<br><br>Prompt the user for their password, then store the response in the `UserPassword` variable. | Entered string written to `UserName`.<br><br>Entered string written to `UserPassword`. |

| Input | Process | Output |

| :--- | :--- | :--- |

| *(none — the values are hardcoded)* | Write the hardcoded value into the `StoredUN` variable.<br><br>Write the hardcoded value into the `StoredPW` variable. | `StoredUN`<br><br>`StoredPW` |

| Input | Process | Output |

| :--- | :--- | :--- |

| `UserName`<br><br>`StoredUN`<br><br>`UserPassword`<br><br>`StoredPW` | Set a `bValid` boolean to False.<br><br>Compare `UserName` with `StoredUN`.<br><br>IF `UserName` = `StoredUN` THEN compare `UserPassword` with `StoredPW`.<br><br>IF those ALSO match THEN set `bValid` to True. | `bValid` |

The Process column for *Validate User* lists the actual decision steps — not just "check the login". **That** is what scores in the upper bands.

| | Input | Process | Output |

|---|---|---|---|

| **❌ Wrong** | `UserName`, `StoredUN`, `UserPassword`, `StoredPW` | Check the login | `bValid` |

| **✅ Right** | `UserName`, `StoredUN`, `UserPassword`, `StoredPW` | 1. Set `bValid` = False. 2. Compare `UserName` with `StoredUN`. 3. If equal, compare `UserPassword` with `StoredPW`. 4. If both match, set `bValid` = True. | `bValid` |

- The Right version shows each comparison and decision. A marker can only credit logic that is visible.

>| From your **DFD** — the data flowing into a process becomes the Input column, and the data flowing out becomes the Output column. The IPO chart details the process in between.