← IGCSE Computer Science Paper 1

Barcodes compared with QR codes

A barcode stores a short number in one dimension of lines; a QR code stores much more data in two dimensions of squares and can be read by a camera from any angle.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 9

Understanding Barcodes compared with QR codes in IGCSE Computer Science Paper 1

What it does: A laser beam sweeps in one direction across the lines, so the barcode has to be facing the right way. A QR code has position squares in its corners, so the camera can work out its orientation and read it from any angle. A QR code uses a grid of squares in two dimensions, so it holds far more data than a barcode, which usually holds just a short number. Barcodes only store a short number. The shop's database looks up the name and price using that number. The QR code is two-dimensional, so it does not need to be lined up in a straight line like a 1D barcode.

Common mistakes: A QR code is 2D and a barcode is 1D, so qr_dims is greater than bar_dims. The comparison should use > so it prints True. A barcode stores data in one dimension (a row of lines), so bar_dims should be 1. Two dimensions describes a QR code.

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Learning

Duo

Which code stores data in only ONE dimension (a row of lines)?

BarcodeQR code

Matches

A barcode stores a web link in a grid of squares

↓

A barcode uses 1D lines and holds only a short number. A grid of squares and much more data describe a QR code.

Applying

Meanings

Term

1D barcode vs 2D QR code

Meaning

A barcode stores a short number in one dimension of lines; a QR code stores much more data in two dimensions of squares and can be read by a camera from any angle.

Practice

Barcode: 1D lines, short number

Testing

Gaps

barcode.dimensions ←

Check Answer

Spots

2qr_dims = 2

3print(qr_dims < bar_dims)

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Quick Questions

1. Which code stores data in only ONE dimension (a row of lines)?

A. QR code

B. Barcode ✓

A barcode is 1D: the data runs left to right in lines of different widths. A QR code is 2D.

2. Which code can store much more data, such as a web address or a paragraph of text?

A. QR code ✓

B. Barcode

A QR code uses a grid of squares in two dimensions, so it holds far more data than a barcode, which usually holds just a short number.

3. A barcode on a packet of crisps usually stores...

A. A short number that identifies the product ✓

B. The whole description, price and photo of the product

Barcodes only store a short number. The shop's database looks up the name and price using that number.

4. Which statement about reading a QR code is correct?

A. A camera can read it from any angle ✓

B. It must be scanned in a straight line across the lines

QR codes have three corner squares that show the scanner which way round the code is, so it can be read from any angle. A basic barcode scanner needs the beam to cross the lines.

5. Which scanner is traditionally used to read a barcode at a supermarket till?

A. A 3D scanner that measures the shape of the packet

B. A laser scanner that sweeps a beam across the lines ✓

A laser scanner shines a red beam across the barcode and measures the light reflected back from the dark and light lines.

Match the Pairs

1D barcode → Stores a short number using one dimension of vertical lines, so it holds only a small amount of data

2D QR code → Stores much more data using a grid of squares in two dimensions, so it can hold web links and text

A laser scanner reads a barcode by sweeping a beam across the lines, so the barcode must be lined up with the scanner → laser scanner + 1D barcode

A camera-based scanner captures an image of a QR code, so it can read the code at any angle → camera + 2D QR code

A barcode stores a web link in a grid of squares → A barcode uses 1D lines and holds only a short number. A grid of squares and much more data describe a QR code.

A QR code is 1D, so it must be scanned in a straight line → A QR code is 2D, using width and height. Because of this it can be scanned from any angle.

Key Term

1D barcode vs 2D QR code

A barcode stores a short number in one dimension of lines; a QR code stores much more data in two dimensions of squares and can be read by a camera from any angle.

Fill in the Blanks

1. barcode.dimensions ← 1

Hint: Type the number of dimensions a barcode uses to store its lines.

2. qrCode.dimensions ← 2

Hint: Type the number of dimensions a QR code uses to store its squares.

3. IF dataLength > 20 THEN code ← "QR" ENDIF

Hint: Type the kind of code that can store a large amount of data.

4. qrCode.readAngle ← "any"

Hint: Type the word describing which scanning angles a QR code can be read from.

5. qrScanner.uses ← "camera"

Hint: Type the device a QR code scanner uses to capture an image of the code.

Spot the Error

Question 1

A bar_dims = 1

B qr_dims = 2

C print(qr_dims < bar_dims)

Line C — A QR code is 2D and a barcode is 1D, so qr_dims is greater than bar_dims. The comparison should use > so it prints True.

Question 2

A bar_dims = 2

B qr_dims = 2

C print("Barcode dims:", bar_dims)

Line A — A barcode stores data in one dimension (a row of lines), so bar_dims should be 1. Two dimensions describes a QR code.

Question 3

A def can_store_url(code)

B return code == "QR"

C print(can_store_url("QR"))

Line A — A function definition must end with a colon. It should be def can_store_url(code):

Question 4

A code = "QR"

B reader = "camera"

C if reader = "camera":

D print("Can read QR")

Line C — A single = assigns a value, but an if statement needs a comparison. It should be if reader == "camera": so the camera is checked.

Question 5

A data = "www.cloodit.com"

B code = "barcode"

C print("Use", code, "for a URL")

Line B — A barcode only holds a short number, so it cannot store a web address. A QR code stores much more data, so code should be "QR".

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