An Operating Systems Vade Mecum

GLOSSARYMany standard English words are used in a technical sense in this book. Careful andconsistent use of these terms is a worthwhile habit to cultivate. Alternative expressionsthat you might find in the literature are also given here. This glossary should be taken asa guide to the sense in which I have used these terms rather than as a prescription fortheir proper use. Since there are many different kinds of operating systems, not all ofthese terms have meaning in all implementations.Abort. To announce that a transaction has failed.Absolute file name. A file name that indicates where a file lies with respect to the rootof the file structure.Absolute. (1) With respect to a standard reference point. For example, an absolute filename is given as a path from the root of the file tree. (See Relative.) (2) Certain to betrue and up to date. For example, each disk block can include absolute information identifyingthe file to which it belongs. (See Hint.)Abstraction. Higher-level resources created out of lower-level ones. Details of thelower-level structures are hidden, and higher-level structures are introduced. (See Physicaland Virtual.)Access control. A policy that determines the forms of access that subjects may makeover objects.Access list. A list of all the subjects that can access a given object and the privileges ofeach one.Access matrix. A matrix with one row for each subject and one column for each objectthat shows the privileges each subject has over each object.Access mode. The manner in which a subject accesses an object, such as reading asopposed to writing.328