1. Data Storage In today’s lesson we will look at:
What we mean by computer storage
The units used to describe computer storage
Types of storage in the computer – primary and secondary
We will mainly focus on secondary storage:
Storage media
Choosing media

2. Data Storage
Why do companies and individuals do their work on computers?
It allows them to process data more quickly and produce high-quality information and presentations
It allows them to store the results and re-use them
How do we describe how much data we have, or require?
The basic unit of storage size is the byte
One byte isn’t much use, so we have kilobytes, megabytes, gigabytes and now terabytes

3. Data Storage One byte would typically store: a number from 0 - 255
one character (a letter or a digit) in a word-processed document
one third of a pixel (or dot) in a photo-quality picture
a quarter of one forty-four-thousandth of a second of CD-quality music
very little of a video!

4. Types of Storage Primary storage (e.g. RAM):
Volatile - i.e. contents are lost without power
Use to store data while it is being processed
Fast - access time measured in nanoseconds for PCs
Relatively expensive - 1Gb DDR RAM costs about £20
Secondary storage (e.g. hard disc):
Non-volatile, usually magnetic media - data are stored without power
Used for permanent storage of data after it has been “saved”
Slower - access time of around 8ms
Cheaper, e.g. 1Tb for £50

5. Common Storage Media
Most storage media are either optical or magnetic:
Hard disc
Floppy disc (very old-fashioned now!)
CD-ROM / CD-R / CD-RW
DVD-RAM / DVD-R / DVD-RW
Memory cards – e.g. SD, Compact Flash, etc.
USB memory sticks
The price of these media falls all the time, and the capacities get larger and larger.

6. Choosing Media
If you wanted to store a file, what would affect your choice of media?
The type of file and what you plan to do with it
The size of the file
Whether you need to change it again
If you’re sending it to someone else:
what they want to do with the file
how it’s getting there – is your medium small and robust enough for you to post it?
whether they have the hardware to access it

7. Cloud Storage
Faster internet connections have made it possible to transfer files quickly and store them elsewhere.
Cloud storage services such as OneDrive, Google Drive and Dropbox allow free storage for files, often with apps to allow mobile access.
Files stored in “the cloud” can also be shared – either with specified users, or publicly.
Some services synchronise with folders on your PC so that the process of storing files in the cloud is transparent – you don’t know that you’re doing it!

8. Cloud Storage Access from different locations and devices
Security - documents are not on your computer
…and possibly not in your country, which could cause problems, e.g. with the DPA
You are dependent on your internet connection
…and the service provider; services can close down
Performance – saving and loading files will be slower than saving to a hard disc
Access from different locations and devices
Can collaborate and share documents
Often free-of-charge
No needs to install
Requires no disc space and cheaper local devices

9. Files and Folders The data you save will be stored in a file
Why is it important that you give your files sensible names?
What makes a sensible name?
A file has a file type, which tells the computer which program is needed to open it
What are .jpg, .doc, .xls files, etc.
Files can be stored in folders
Why do we use folders?
What is a path?

10. Copying and Moving Files
You can move or copy files, either by using the menus or by dragging them
You need to be careful, though...
If you drag a file to another folder on the same drive, device or card, it will be moved
If you drag to another drive, device or card, a copy will be made...
...except that for some types of file (e.g. programs), a shortcut will be created
a shortcut is a link to a file, so you need to be careful not to delete the original file

11. ICT Exams and Coursework
To evidence that you understand how to correctly store your work, you are often asked to include a screen-shot of your files, so...
You must create a sensible folder structure
You must give your files sensible names
You must know how to create a “screen-shot” to show that you’ve done this
NB. iOS gives you no access to the filing system, so you can’t practice this on an iPad.