Functions of Distributed Operating Systems
A distributed operating system is a system that spreads the load over multiple computer hardware servers. This type of OS provides better performance and availability because it is distributed across multiple components.
Functions of a Distributed Operating System
- Control of Multiple Sites: A distributed operating system spreads the load over multiple computer hardware servers. This provides better performance and availability.
- Client/Server Model: A common way of organizing software to run on distributed systems is to separate functions into two parts: clients and servers. A client is a program that uses services that other programs provide. The programs that provide the services are called servers. The client makes a request for a service, and a server performs that service.
- User Access to Multiple Sites: A distributed operating system looks to its users like an ordinary centralized operating system but runs on multiple, independent central processing units (CPUs). These systems are referred to as loosely coupled systems where each processor has its own local memory and processors communicate with one another through various communication lines, such as high-speed buses or telephone lines.
Security Features in Networking Systems
- Passwords: A password is a secret word or string of characters used for user authentication to prove identity or for access approval to gain access to an operating system. Most network operating systems let you establish password policies, such as requiring that passwords have a minimum length and include a mix of letters and numerals.
- Access Control: This is a process to determine “Who does what to what,” based on a policy. It controls access of who gets in and out of the system and who uses what resources, when, and in what amounts. Access control restricts access to a system or system resources based on something other than the identity of the user.
- User Permissions: The authorization given to users that enables them to access specific resources on the network, such as data files, applications, printers, and scanners. User permissions also designate the type of access; for example, can data only be viewed (read only) or can they be updated (read/write). Also called “user rights,” “user authorizations,” and “user privileges.”
Numbering Systems in Computer Systems
- Binary: Computers have a numbering system with only two digits: 0 and 1. 0 = off, 1 = on. They are called binary numbers (bin means two). They follow the same basic rules that decimal numbers do as in Start with 0, increment to 1, then go back to 0 and increment the next column to the left. e.g., bin 0 = dec 0; 1=1; 10=2; 11=3.
- Hexadecimal: This uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F (or alternatively a–f) to represent values ten to fifteen. Hexadecimal offers us a convenient “shorthand” for binary numbers. If we were to represent a byte of data in binary, it would require 8 digits, e.g., 11111111. However, that same byte of data could be represented in hexadecimal in just two digits, e.g., FF.
- ASCII: With the advent of computer systems which used 0’s and 1’s, there was a need to translate between the alphabet the humans use and the digital format that computers use. This resulted in the American Standard Code for Information Interchange (ASCII). It assigned a value to every letter and number in the English alphabet. Uppercase L is ASCII 76. ASCII uses 8 bits (1 byte). Therefore, 256 different characters or codes can be represented in the ASCII format.
Input, Output, and Storage Devices
- Input Devices: An input device is any hardware device that sends data to the computer. Input devices convert the user’s actions and analog data (sound, graphics, pictures) into digital electronic signals that can be processed by a computer.
- Output Devices: Output devices are hardware devices that display or present information from a computer.
- Storage Devices: Also referred to as storage media, or a storage medium, a storage device is a hardware device capable of holding information. There are two storage devices used in computers: a primary storage device such as computer RAM and a secondary storage device such as a computer hard drive. The secondary storage could be a removable, internal, or external storage.