Understanding Gray Code, DVD-RW, HSDPA, and User Access
Understanding Key Digital Concepts
Gray Code (Reflected Binary Code)
The reflected binary code, or Gray code, named after researcher Frank Gray, is a binary numeral system where two successive values differ in only one digit. The Gray code was originally designed to prevent spurious signals from electromechanical switches. It is currently used to facilitate error correction in communication systems, such as certain cable television systems and digital terrestrial television.
A code is called Johnson (Johnson-Mobius) if it is a continuous and cyclic binary code (like the Gray code) whose coding capacity is given by 2n, where n is the number of bits. The sequence is simple: shift all bits one to the left, and the least significant bit is the complement of the bit that was previously furthest to the left.
Given the simplicity of the design, counters that track the issue in this code are used in the control of simple, high-speed digital systems. It provides greater protection against errors but is less memory-efficient than binary-coded decimal. To encode the decimal digits, 5 bits are needed.
DVD-RW Technology
DVD-RW, or DVD recorder, can read, write, and rewrite images, audio, and data disks with gigabytes of capacity, ranging from 650 MB to 9 GB.
HSDPA (3.5G)
HSDPA (High-Speed Downlink Packet Access), also known as 3.5G, is an evolution of UMTS (Universal Mobile Telecommunications System) third generation (3G), and is designed to offer higher bandwidth communications networks for mobile phones. This is a pioneering technology for next-generation wireless communications through these devices, such as 4G, which is currently under study and development (although an intermediate technology, 3.9G, is very probable).
Computer Networks and Resource Sharing
Computer networks enable the sharing of programs, information, and resources among connected machines (PCs). These connected machines are continually changing and innovating, which enhances this process and increases its resources and capabilities.
From a computer networking perspective, sharing computer resources involves setting up a network so that computers can use resources from other computers using the network as a means of communication. All kinds of resources can be shared, with the most common being printers, disk drives, and internet access.
User Accounts and Access
In the context of computers, a user is someone who uses a computer system. To enable users to have security, system access, resource management, etc., those users must be identified. For one to be identified, the user needs a user account and a username, in most cases associated with a password. Users use a user interface to access the systems; the identification process is known as user ID or user access to the system (logging in).
Users are characterized by being people using a system without the necessary experience required to understand the system (as opposed to technical, hacker, or other profiles known to have system knowledge).
Permissions and Privileges
Permissions and privileges relate to the level of access to information and system actions and operations that users can perform. They have been defined around some roles and user profiles that can be established, in general or by Secretariat.
To facilitate the operation of the system, it is necessary to define roles, since all the people who will interact with the same shall have access to different options according to their work. Having defined a role, privileges should be allocated to execute system options. This option is for users to whom access is assigned; it is recommended that only the administrator user have this access.