← IGCSE Computer Science Paper 1

Keyboard

An input device where pressing a key completes a circuit. The controller identifies the key and sends its character code to the computer, so text and commands can be entered.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 3, IGCSE Computer Science 0478 — 4.1 Types of Software and Interrupts — Module 47

Understanding Keyboard in IGCSE Computer Science Paper 1

What it does: This shows the order of events: the key press completes the circuit, then the controller works out which key it was. The keyboard sends a character code for the key, and the computer then processes it, for example by showing a letter on screen. Keyboards are used to enter text and commands. Scanning a 3D object needs a 3D scanner.

Common mistakes: Pressing a key is what completes the circuit and starts the process. Line 1 should be: WHEN a key is pressed. Pressing a key closes the circuit under it, it does not leave it open. Line 2 should be: circuit ← CLOSED.

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 240–251) and word search (Modules 240–261).

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Learning

Duo

What happens inside a keyboard when you press a key?

The key press shines a laser at the deskThe key press completes a circuit

Matches

Pressing a key opens the circuit, so the keyboard sends the code

↓

Pressing a key closes (completes) the circuit, not opens it. The completed circuit is what lets the keyboard detect the key press.

Applying

Meanings

Term

keyboard

Meaning

An input device where pressing a key completes a circuit. The controller identifies the key and sends its character code to the computer, so text and commands can be entered.

Practice

IF keyPressed = TRUE THEN

Testing

Gaps

circuit ←

Check Answer

Spots

1WHEN a key is pressed

2WHEN a key is released

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Quick Questions

1. What happens inside a keyboard when you press a key?

A. The key press shines a laser at the desk

B. The key press completes a circuit ✓

Pressing a key closes (completes) a circuit under that key. This is how the keyboard detects the press.

2. Which part of the keyboard works out which key was pressed?

A. The keyboard controller ✓

B. The speaker

The keyboard controller identifies which circuit was completed and so which key was pressed. A speaker is an output device.

3. What does the keyboard send to the computer after a key is pressed?

A. The character code for that key ✓

B. A picture of the key

The keyboard sends a character code for the key, and the computer then processes it, for example by showing a letter on screen.

4. A keyboard is which type of device?

A. Output device

B. Input device ✓

A keyboard sends data into the computer, so it is an input device. Output devices such as screens and printers send data out.

5. Which is a use of a keyboard?

A. Typing text and commands ✓

B. Scanning a 3D object to make a model

Keyboards are used to enter text and commands. Scanning a 3D object needs a 3D scanner.

Match the Pairs

keyboard → An input device where pressing a key completes a circuit and sends that key's character code to the computer

character code → The number the keyboard sends to the computer to show which key was pressed

Pressing a key closes a circuit, so the keyboard controller can identify which key was pressed → key press -> circuit closed -> controller identifies key

A keyboard is used to enter text and commands by sending a key's character code to the computer → press 'A' -> code sent -> 'A' appears on screen

Pressing a key opens the circuit, so the keyboard sends the code → Pressing a key closes (completes) the circuit, not opens it. The completed circuit is what lets the keyboard detect the key press.

The computer works out which key was pressed by checking the screen → The keyboard controller identifies the key and sends its character code to the computer. The screen is an output device and plays no part in identifying keys.

Key Term

keyboard

An input device where pressing a key completes a circuit. The controller identifies the key and sends its character code to the computer, so text and commands can be entered.

Fill in the Blanks

1. IF keyPressed = TRUE THEN circuit ← CLOSED ENDIF

Hint: Type the state the circuit is put in when a key is pressed down.

2. character ← "A" keyCode ← ASC(character)

Hint: Type the function that gives the character code of a character.

3. keyCode ← ASC("A") SEND keyCode TO computer

Hint: Type the variable that holds the character code sent to the computer.

4. INPUT text OUTPUT text

Hint: Type the keyword that reads what the user types on the keyboard into a variable.

5. keyCode ← 72 character ← CHR(keyCode)

Hint: Type the function that turns a character code back into its character.

Spot the Error

Question 1

A WHEN a key is pressed

B WHEN a key is released

C controller identifies key

D character code is sent

Line B — Pressing a key is what completes the circuit and starts the process. Line 1 should be: WHEN a key is pressed.

Question 2

A WHEN key is pressed

B circuit ← OPEN

C code ← IDENTIFY(circuit)

D SEND code TO computer

Line B — Pressing a key closes the circuit under it, it does not leave it open. Line 2 should be: circuit ← CLOSED.

Question 3

A key ← 'H'

B circuit ← CLOSED

C code ← ASCII(circuit)

D SEND code TO computer

Line C — The character code belongs to the key that was identified, not to the circuit. Line 3 should be: code ← ASCII(key).

Question 4

A INPUT name FROM speaker

B message ← 'Hello ' + name

C OUTPUT message

Line A — A keyboard is the input device used to type text. A speaker is an output device. Line 1 should be: INPUT name FROM keyboard.

Question 5

A FOR i ← 1 TO 3

B OUTPUT letter TO keyboard

C text ← text + letter

D NEXT i

Line B — A keyboard is an input device, so data comes FROM it and cannot be output TO it. Line 2 should be: INPUT letter FROM keyboard.

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