Where goes the data deleted?
The MIT students were able to recover data from hard disk because deleting a file on a computer does not normally remove the files actual data.
Solutions:
There are only two ways to ensure data is fully removed fromk ypur hard disk by either physically destroying the hard disk or by using special disk wiping software
If the intention is to reuse the disk , a less exciting solution is to use specialist disk wiping or secure deletion software.

Storing data : Bits and Bytes

Representing all of its data internally as binary digits, ones and zeroes. these ones anfd zeroes are known as bits
Eight bits are gruped together, bytes themselves are grouped into increasingly larger units called kilobytes,megabytes ,gigabytes and terabytes
A byte might represent in a letter in a document, or it might present the colour of a pixel on the Screen
ASCII CODE
ASCII is a standard coding scheme for representing text using the english alphabet,each byte of data represents a single character
ASCII uses one byte per character, the maximum numer of characters ASCII can represent is 128
Unicode: Unicode uses up to 4 bytes to represent each character, allowing many thousands of characters to be represented
The modern opeerating systems are windows, windows 7, Mac OS, and Linux, they use UNICODE

Plain Text
ASCII and unicode are both examples of plain text standards
Plain text files are usually saved by programms known as text editors

Graphic Standards:
Computer graphics are represented as bits and bytes just like all other computer data. Each pixel in an image uses three bytes of storage space.