A computer system consists of a set of hardware and software objects. The protection domain is a set of pairs of objects and rights needed to access those objects. An access matrix is a representation of protection domains. (It is more conceptual than actual however.) Each row specified the object, and a right that can be performed as…
User authentication is the act of verifying the identity of a person who wishes to connect to a computer or a network. This can be done in several ways, but most commonly is through a user name and password. For more complex, or sensitive systems, you may be asked to use two (or more) factor authentication….
Computer security is the freedom from theft of or damage to hardware, software, or information, and from disruption or misdirection of services. Protection is the set of mechanisms and policies that guarantee computer security, including the confidentiality, integrity, availability, and authenticity of all data and services. Common types of compromised computer security Information disclosure Information modification Information…
Two conditions must hold for a deadlock to occur with reusable resources: Hold and wait: A process is already holding one resource and is requesting another resource. Circular wait: A process must issue a resource request that closes a cycle involving at least two processes and two resources. Deadlock is structurally impossible if either of…
One approach to dealing with deadlocks is to allow deadlocks to occur and to provide means for detection and recovery. Recovery from a deadlock can be accomplished by destroying one or more of the processes involved in the deadlock, or by removing some of the resources held by the deadlocked processes. However, this causes a…
Errors can occur for several reasons when performing an IO operation. On a read of a disk you could have: a failed write operation the sector go bad due to age/use Additionally you could have issues with data being corrupted during transmission, especially over a long network. Therefore a parity bit is added to a series…
Hard disks are still the most popular form of persistent data storage. Inside a HDD is a series of round platters (disks) that spin. This is a magnetic surface which is read and written to. Most modern HDDs spin in the 7200RPM range or higher. Each platter is made up of a series of tracks,…
A buffer is a register or an area of main memory used to hold data generated by a producer process or an input device and removed from the buffer at a later time by a consumer process or an output device. Depending on the intended use, a single buffer can hold one character at a time or…
