# Computing - Input & Output Devices

> Source: https://ollybritton.com/notes/a-level/computing/topics/input-and-output-devices/ · Updated: 2024-08-25 · Tags: computing, school, a-level

## See Also
- [Computing - Storage Devices](https://ollybritton.com/notes/a-level/computing/topics/storage/)

## Flashcards
### 2020-11-30
##### What's an example usage of barcodes??
* Airline baggage tracking
* Product labelling
* Parcel delivery and shipment
* Ticketing and identification

##### What concept allows barcode readers to work??
Reflected light

##### What does a black bar represent in a barcode??
$$
0
$$

##### Why does black represent $0$ in barcodes??
Black reflects less light.

##### What does a white bar represent in a barcode??
$$
1
$$

##### Why does white represent $1$ in barcodes??
White reflects more light.

##### What does UPC-A stand for??
Universal Product Code Version A

##### What is UPC-A??
A barcode standard.

##### What does EAN stand for??
European Article Number

##### What are the two common standards for product barcodes??
* UPC-A
* EAN

##### What are "Code 128" barcodes used for??
Transport and shipment tracking.

##### ![PHOTO UPC-A BARCODE](paste-ccef29c7db5a913f20486657fd8a12a43b87ff5b.jpg) What does the large left number represent??
The manufacturer number.

##### ![PHOTO UPC-A BARCODE](paste-ccef29c7db5a913f20486657fd8a12a43b87ff5b.jpg) What does the large right number represent??
The product number.

##### ![PHOTO UPC-A BARCODE](paste-ccef29c7db5a913f20486657fd8a12a43b87ff5b.jpg) What is the far right number??
$$
9
$$

##### ![PHOTO UPC-A BARCODE](paste-ccef29c7db5a913f20486657fd8a12a43b87ff5b.jpg) This image contains identical bars at the beginning, middle and end. What are these called??
Guard bars.

##### ![PHOTO UPC-A BARCODE](paste-ccef29c7db5a913f20486657fd8a12a43b87ff5b.jpg) Why is the left hand side and the right hand side the exact opposites??
So that the orientation doesn't matter.

##### If you have $0010$ on one side of a barcode, what do you have on the other??
$$
1101
$$

##### What does $QR$ stand for??
Quick Response

##### What does $CCD$ stand for??
Charge-Coupled Device

##### What does $CMOS$ stand for??
Complementary Metal Oxide Semiconductor

##### What is better: A $CCD$ or $CMOS$??
A $CCD$.

##### What is a $CCD$ or a $CMOS$??
The sensor in a camera.

##### What are the two types of camera sensors??
* CCD
* CMOS

##### What happens when a camera's shutter opens??
The light hits the sensor and the light values are represented as binary values.

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