•The second phase of the digital revolution materialized when the Internet was opened to public use

–E-mail

–Bulletin boards

–Chat groups

–Online social networks

• A computer network is a group of computers linked by wired or wireless technology to share data and resources.

• The Web is a collection of linked documents, graphics, and sounds that can be accessed over the Internet.

• Cyberspace is a term that refers to entities that exist largely within computer networks.

• Digitization is the process of converting text, numbers, sound, photos, and video into data that can be processed by digital devices.

• Before cloud computing, most computers ran software based locally. With cloud computing, you can use your browser to access, word processing applications that run on the Internet instead of software that you have installed on your local hard disk. Cloud computing gets its name from the diagrams that show storage as being part of a cloud.

• •Technological convergence is a process by which several technologies with distinct functionalities evolve to form a single product. Convergence tends to offer enhanced functionality and convenience

• Data refers to the symbols that represent people, events, things, and ideas. Data can be a name, a number, the colors in a photograph, or the notes in a musical composition.

• Data Representation refers to the form in which data is stored, processed, and transmitted.

• Devices such as smartphones, iPods, and computers store data in digital formats that can be handled by electronic circuitry.

• Digitization is the process of converting text, numbers, sound, photos, and video into data that can be processed by digital devices

• The digital revolution has evolved through four phases, beginning with big, expensive, standalone computers, and progressing to today’s digital world in which small, inexpensive digital devices are everywhere

• The 0s and 1s used to represent digital data are referred to as binary digits – from this term we get the word bit which stands for binary digit

• A bit is a 0 or 1 used in the digital representation of data.

• A digital file, usually referred to simply as a file, is a named collection of data that exits on a storage medium, such as a hard disk, CD, DVD, or flash drive.

• Character data is composed of letters, symbols, and numerals that are not used in calculations. Examples of character data include your name, address, and hair color. Character data is commonly referred to as “text.”

• Digital devices employ several types of codes to represent character data, including ASCII, Unicode and their variants. ASCII (American Standard Code for Information Interchange, pronounced “ASK ee”) requires seven bits for each character. The ASCII code for an uppercase A is 1000001

• Extended ASCII is a superset of ASCII that uses eight bits for each character. For example, Extended ASCII represents the uppercase letter A as 01000001. Using eight bits allows Extended ASCII to provide codes for 256 characters

• Unicode (pronounced “YOU ni code”) uses sixteen bits and provides codes or 65,000 characters. This is a bonus for representing the alphabets of multiple languages

• ASCII codes are used for numerals, such as Social Security numbers and phone numbers. Plain, unformatted text is sometimes called ASCII text and is stored in a so-called “text file” with a name ending in .txt. On Apple devices these files are labeled “Plain Text”; in Windows, these files are labeled “Text Document . ASCII text files contain no formatting. To create documents with styles and formats, formatting codes have to be embedded in the text.

• Microsoft Word produces formatted text and creates documents in DOCX format. iWork Pages produces documents in PAGES format. Adobe Acrobat produces documents in PDF format. HTML markup language used for Web pages produces documents in HTML format.

• All of the data stored and transmitted by digital devices is encoded as bits. Terminology related to bits and bytes is extensively used to describe storage capacity and network access speed. The word bit, an abbreviation for binary digit, can be further abbreviated as a lowercase b. A group of eight bits is called a byte and is usually abbreviated as an uppercase B.

• When reading about digital devices, you’ll frequently encounter references such as 50 kilobits per second, 1.44 megabytes, 2.8 gigahertz, and 2 terabytes. Kilo, mega, giga, tera, and similar terms are used to quantify digital data.

• Use bits for data rates, such as Internet connection speeds, and movie download speeds. Use bytes for file sizes and storage capacities

• To reduce file size and transmission times, digital data can be compressed. Data compression refers to any technique that recodes the data in a file so that it contains fewer bits. Compression is commonly referred to as “zipping”.

• Compression techniques have two categories: lossless and lossy. Lossless compression provides a way to compress data and reconstitute it into its original state; uncompressed data stays exactly the same as the original data. Lossy compression throws away some of the original data during the compression process; uncompressed data is not exactly the same as the original.

• Software for compressing data is sometimes referred to as a compression utility or a zip tool. On laptops and desktop computers, the compression utility is accessed from the same screen used to manage files. The process of reconstituting files is called extracting or unzipping. Compressed files may end with a .zip, .gz, .pkg, .tar or.gz