What mistakes do students make with Input/output?

Confusing authentication with validation. Put it right by stating that authentication compares entered details with stored records. Thinking a lookup means checking the password only. Put it right by describing both stages. Assuming authentication guarantees the data is accurate. Put it right by stating that authentication controls access, not data truth.

What are the exam tips for Input/output in Computer Science Pearson Edexcel GCSE?

State the purpose of authentication before describing the ID and password process. When writing code, show the lookup step and the comparison, and make the access decision depend on both matching. Use terms such as stored record, lookup, credentials and access granted or denied accurately.

Pearson Edexcel · GCSE · Computer Science

Course version: 1CP2 · Version from Sept 2020

Understand the need for and be able to write programs that implement…

Full specification wording

Input/output: 6.4.4 understand the need for and be able to write programs that implement authentication (ID and password, lookup)

Authentication confirms that a user is who they claim to be before allowing access.

Checked against the Pearson Edexcel 1CP2 specification (opens in a new tab) on 10 November 2026.

Point 2 of 2
3 key terms

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

Authentication confirms a user's identity before granting access to a system or its data.
A typical method collects an ID and a password from the user.
A lookup searches stored records for the supplied ID and retrieves the associated stored password or credential.
The program compares the entered password with the stored password and grants access only when both the ID and password match.
If the ID is not found or the password does not match, the program denies access and may allow a limited number of retries.
Authentication is implemented using selection, iteration and data structures such as lists or dictionaries.

Common mistakes and how to put them right

Confusing authentication with validation.
Put it right by stating that authentication compares entered details with stored records.
Thinking a lookup means checking the password only.
Put it right by describing both stages.
Assuming authentication guarantees the data is accurate.
Put it right by stating that authentication controls access, not data truth.
Writing code that grants access when either the ID or the password matches.
Put it right by testing the combined condition.

Exam tips

State the purpose of authentication before describing the ID and password process.
When writing code, show the lookup step and the comparison, and make the access decision depend on both matching.
Use terms such as stored record, lookup, credentials and access granted or denied accurately.

Try the lesson

The start of the Input/output: 6.4.4 understand the need for and be able to write programs that implement authentication (ID and password, lookup) lesson, made from checked teaching notes for this specification point.

Have a go first

A program stores each user's ID and password as a record in a list. A user types in an ID to log in. Before any password can be checked, what must the program do with the typed ID?

Tip: press 1 to 4 to choose

Listen

Authentication confirms that a user is who they claim to be before allowing access. A common method asks for an ID and a password, then performs a lookup: the program searches stored records for the supplied ID and compares the stored password with the one entered. If both match, access is granted; otherwise access is denied and the user may be asked to try again. The need is to protect systems and data from unauthorised use. Programs implement this with selection, iteration and data structures such as lists or dictionaries. A lookup may also retrieve other details linked to the ID. Authentication differs from validation: validation checks the format of input, while authentication checks identity against stored credentials. A strong answer earns marks for these points. Authentication confirms a user's identity before granting access to a system or its data. A typical method collects an ID and a password from the user. A lookup searches stored records for the supplied ID and retrieves the associated stored password or credential. The program compares the entered password with the stored password and grants access only when both the ID and password match. A common slip: Confusing authentication with validation: validation checks that input is in a sensible format, while authentication checks identity against stored credentials. Instead, stating that authentication compares entered details with stored records. Exam tip: State the purpose of authentication before describing the ID and password process.

See it

A flowchart running top to bottom. The first box says 'Collect ID and password' and leads to a box saying 'Lookup stored records for supplied ID'. This leads to a decision diamond asking 'ID found?'. If the answer is No, the path goes to a box saying 'Access denied'. If the answer is Yes, the path goes to a decision diamond asking 'Entered password matches stored password?'. If the answer is No, the path goes to 'Access denied'. If the answer is Yes, the path goes to a box saying 'Access granted'. From 'Access denied', a final box says 'May be asked to try again'. — It shows the ID and password authentication process: collecting credentials, looking up the stored record, comparing the password, and granting or denying access.

Key words

Say what each word means before you turn the card.

Authentication

Try answering aloud or in your head before turning the card.

ID and password

Try answering aloud or in your head before turning the card.

Lookup

Try answering aloud or in your head before turning the card.

See every definition

Authentication: Confirms that a user is who they claim to be before allowing access to a system or its data.
ID and password: Details collected from the user, where the program searches stored records for the supplied ID and compares the stored password with the one entered.
Lookup: Searches stored records for the supplied ID and retrieves the associated stored password or credential.

Label the diagram

Some boxes have lost their names. Pick the right name for each number.

The diagram again, with 3 boxes numbered instead of named. A flowchart running top to bottom. The first box says 'Collect ID and password' and leads to a box saying 'Lookup stored records for supplied ID'. This leads to a decision diamond asking 'ID found?'. If the answer is No, the path goes to a box saying 'Access denied'. If the answer is Yes, the path goes to a decision diamond asking 'Entered password matches stored password?'. If the answer is No, the path goes to 'Access denied'. If the answer is Yes, the path goes to a box saying 'Access granted'. From 'Access denied', a final box says 'May be asked to try again'.

1Box 1
2Box 2
3Box 3

0 of 3 labelled

There is more to this lesson

The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.

Carry on with the full lesson

A week of Premium from your first lesson · Then the free plan continues · No card, no charge

Test your understanding of Input/output: 6.4.4 understand the need for and be able to write programs that implement authentication (ID and password, lookup)

Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.

Take topic quiz

A week of Premium from your first lesson · Then the free plan continues · No card, no charge

Understand the need for and be able to write programs that implement…