Data Capacity And Calculating Capacity Requirements Ocr

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Exam code:J277

Data Capacity & Calculating Capacity Requirements

What is data capacity?

Data capacity is the maximum amount of information that a storage device can hold
If you know the capacity of a storage device, you can calculate how much of different data types can be stored
Examples of data that could be stored include text, images and sound files

How do you calculate capacity requirements?

To calculate capacity requirements you need to:
- Know the capacity of the storage device
- Calculate the size of a file (formula)
- Ensure the same units of data storage are used for capacity and size of the file, else convert between units to get them to be the same
- Divide the capacity by size of the file being stored

The image above shows common capacities of storage devices such as hard drives (HDD), USB flash drives, solid state drives (SSD) and optical disks (CD)

Calculating file sizes

Text Files

(Bytes per character) x (Number of characters)

Size of text file =
Bytes per character	1	Based on Extended ASCII character set being used (8 bits)
Number of characters	2000	Including spaces!
1 x 2000	=	2000 bytes = 2 KB

Image Files

(Resolution) x (Colour Depth)

Size of image file =

Resolution

500 x 500

Resolution = Width x Height

Colour Depth

24 bits

24 bits = 3 bytes

(500×500) x 24

(500×500) x 3

6,000,000 bits

750,000 bytes = 75 KB

Sound Files

(Sample Rate) x (Duration in seconds) x (Bit Depth)

Size of sound file =
Sample Rate	10	Samples per second
Duration	30	Seconds
Bit Depth	4	Number of bits stored per sample
10 x 30 x 4	=	1200 bits = 150 bytes

Worked Example

Lyla is a social media influencer. She creates images to be shared on her social media accounts.

Each image has a fixed size of 3 MB. She is storing the images on a USB flash drive which has a capacity of 6 GB.
Calculate how many images can be saved on the storage device. Show your working [2]

How to answer this question:

Convert 6 GB to MB
Divide the capacity in MB by the files size in MB

Answer

6 GB = 6 * 1000 = 6000 MB
6000 / 3 = 2000 images

Computer Science GCES OCR