Barcode scanner

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Quick Questions

Shade in the A or B circle for each question.

1. What does a barcode scanner usually shine across a barcode?

A A stream of ink

B A laser beam

2. Which part of a barcode absorbs the light?

A The black lines

B The white gaps

3. Which part of a barcode reflects the light back to the scanner?

A The black lines

B The white gaps

4. What does the scanner's light sensor turn the pattern of reflected light into?

A Digital data

B A printed receipt

5. The barcode itself stores the product's name and current price.

A False: it stores a number that is looked up in a database

B True: all the details are inside the lines

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1barcode scanner		AAn input device that shines a laser across a barcode and reads the reflected light to get the product number
2reflected light pattern		BThe pattern of light bouncing back from the white gaps but not from the black lines, which the sensor reads
3Black lines absorb light and white gaps reflect it, so the scanner can tell the lines and gaps apart		Cblack = absorbs light, white = reflects light
4The product number read from the barcode is looked up in a database to find the product name and price		DA barcode only stores a product number. The price is found by looking the number up in a database.
5White gaps absorb light and black lines reflect it		Eprice = database.lookup(number)
6The barcode itself stores the price of the product		FThis is the wrong way round. Black lines absorb light and white gaps reflect it.

Definitions

barcode scanner

Fill in the Blanks

Complete each line of code by filling in the missing parts.

Black lines ______ the scanner's light

White gaps _______ light back to the sensor

Sensor turns the pattern into _______ data

Look up the number in a ________ for price

A _____ is shone across the barcode

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A laser SHINES on barcode

B sensor READS reflected light

C black lines REFLECT light

D white gaps REFLECT light

Question 2

A light ← laser.shine()

B pattern ← sensor.write(light)

C number ← decode(pattern)

Question 3

A WHILE items remain

B scan barcode

C price ← lookup(number)

D stock ← stock + 1

E ENDWHILE

Question 4

A scan ← scanner.read()

B number ← decode(scan)

C product ← DB.find(price)

D OUTPUT product.price

Question 5

A IF line IS white THEN

B light ← absorbed

C ELSE

D light ← reflected

Answer Key

Barcode scanner

Section A: Quick Questions

B — A laser beam

A — The black lines

B — The white gaps

A — Digital data

A — False: it stores a number that is looked up in a database

Section B: Match the Pairs

barcode scanner → An input device that shines a laser across a barcode and reads the reflected light to get the product number

reflected light pattern → The pattern of light bouncing back from the white gaps but not from the black lines, which the sensor reads

Black lines absorb light and white gaps reflect it, so the scanner can tell the lines and gaps apart → black = absorbs light, white = reflects light

The product number read from the barcode is looked up in a database to find the product name and price → price = database.lookup(number)

White gaps absorb light and black lines reflect it → This is the wrong way round. Black lines absorb light and white gaps reflect it.

The barcode itself stores the price of the product → A barcode only stores a product number. The price is found by looking the number up in a database.

Section C: Definitions

barcode scanner — An input device that shines a laser across a barcode. Black lines absorb light, white gaps reflect it, and a sensor reads the pattern to get the product number.

Section D: Fill in the Blanks

Black lines absorb the scanner's light

White gaps reflect light back to the sensor

Sensor turns the pattern into digital data

Look up the number in a database for price

A laser is shone across the barcode

Section E: Spot the Error

C — Black lines absorb light, they do not reflect it. The line should be: black lines ABSORB light.

B — The sensor reads the reflected light pattern, it does not write to it. It should be sensor.read(light).

D — Each time an item is scanned and sold, stock goes down. It should be stock ← stock - 1.

C — The database is searched using the product number from the barcode. The price is the result found, so it should be DB.find(number).

A — The IF branch sets light to absorbed, which only happens for black lines. The condition should be IF line IS black THEN.