專業英文導讀
Chapter 7
Key Terms
Key Term / Definition / Page #Authentication / Verification of the sender of a message. / 211
Authentication is the process of determining whether someone or something is, in fact, who or what it is declared to be.
Batch operating system / The operating system used in early computers, in which jobs were grouped before being served. / 195Batch operating system was designed in the 1950s to control mainframe computers.
Bootstrap / The process in which the operating system is loaded into main memory when the computer is turned on. / 194
A very small section of memory is made of ROM and holds a small program called the bootstrap program.
Circular waiting / A condition in an operating system in which all processes and resources involved form a loop. / 207
Circular waiting implies the hold and wait condition. Therefore, these conditions are not completely independent.
Deadlock / A situation in which the resources needed by one job to finish its task are held by other jobs. / 206
Deadlock is a common problem inmultiprocessingsystems,parallel computinganddistributed systems, where software and hardware locksare used to handle shared resources and implementprocess synchronization.
Demand paging / A memory allocation method in which a segment of a program is loaded into memory only when it is needed. / 201
I demand paging the program is divided into pages, but the pages can be loaded into memory one by one, executed, and replaced by another page.
Demand paging and segmentation / A memory allocation method in which a page or a segment of a program is loaded into memory only when it is needed. / 201
Demand paging and segmentation can be combined to further improve the efficiency of the system.
Demand segmentation / A memory allocation method in which a segment of a program is loaded into memory only when it is needed. / 201
In demand segmentation, the program is divided into segments that match the programmer’s view.
Device manger / A component of an operating system that controls access to the input/output devices. / 208
The device manager, or input/output manager, is responsible for access to input/output devices.
Distributed system / An operating system that controls resources located in computers at different sites. / 201
Distributed systems are the study of the communication and coordination patterns of components found in networked computers.
Frame / In paging, memory is divided into equally sized sections called frames. / 200
In paging, memory is divided into equally sized sections called frames.
Graphical user interface(GUI) / A user interface that defines icon and operations on icons. / 197
Designing the visual composition and temporal behavior of a GUI is an important part ofsoftware applicationprogramming in the area ofhuman-computer interaction.
Hold state / The state of a job that is waiting to be loaded into memory. / 203
A program becomes a job when selected by the operating system and brought to the hold state.
Hardware abstraction layer(HAL) / Ahardware abstraction layer(HAL) is anabstraction layer, implemented in software, between the physicalhardwareof acomputerand thesoftwarethat runs on that computer. / 212
TheNetBSDoperating system is widely known as having a clean hardware abstraction layer which allows it to be highly portable.
Job / A Program becomes a job when it is selected for execution. / 202
A program is a job from the moment it is selected for execution until it has finished funning and becomes a program again.
Job scheduler / A scheduler that selects a job for processing from a queue of jobs waiting to be moved to memory. / 204
The job scheduler moves a job from the hold state to the ready state or from the running state to the terminated state.
Kernel / The main part of an operating system. / 210
The kernel is the heart of the UNIX system.
Linux / An operating system developed by Linus Torvalds to make UNIX more efficient when run in an Intel microprocessor. / 211
In 1991, Linus Torvalds, a Finish student at the University of Helsinki at the time, developed a new operating system that is known today as Linux.
Memory management / The component of the operating system that controls the use of main memory. / 197
One of the responsibilities of a modern computer system is memory management.
Microsoft disk operating system / The operating system based on DOS and developed by Microsoft. / 211
In the 1980s Microsoft, under the leadership of Dave Cutler, started development of a new single-user operating system to replace MS-DOS.
Monoprogramming / The technique that allows only one program to be on memory at a time. / 197
Monoprogramming belongs to the past, but it is worth mentioning because it helps us to understand multiprogramming.
Multiprogramming / The technique that allows more than one program to reside in memory while being processed. / 198
In multiprogramming, more than one program is in memory at the same time, and they are executed concurrently, with the CPU switching rapidly between the programs.
Mutual exclusion / A condition imposed by an operating system in which only one process can hold a resource. / 207
Incomputer science,mutual exclusionrefers to the requirement of ensuring that no twoconcurrentprocesses[a]are in theircritical sectionat the same time; it is a basic requirement inconcurrency control, to preventrace conditions.
No preemption / A condition in which the operating system cannot temporarily allocate a resource. / 207
No preemption is that resources cannot be preempted.
Operating system / The software that controls the computing environment and provides an interface to the user. / 194
An Operating system is complex, so it is difficult to give a simple universal definition.
Page / One of a number of equally sized sections of program. / 200
Programs are also divided, into equally sized sections called pages.
paging / A Multiprogramming technique in which memory is divided into equally sized sections called frames. / 200
Paging improves the efficiency of partitioning.
Parallel system / An operating system with multiple CPUs on the same machine. / 196
The need for more speed and efficiency led to the design of parallel systems: multiple CPUs on the same machine.
Partitioning / A technique used in multiprogramming that divides the memory into variable-length sections. / 199
The first technique used in multiprogramming is called portioning.
Process / A program in execution. / 203
A process is a program in execution.
Process scheduler / An operating system mechanism that dispatches the processes waiting to get access to the CPU. / 204
The process scheduler moves a process from one state to another.
Program / A set of instructions. / 202
A program is a nonactive set of instructions stored on disk.
Portability / The quality factor relating to the ease with which a system can be moved to other hardware environments. / 211
Design goals released by Microsoft are extensibility, portability, reliability, compatibility and performance.
Process manager / An operating system component that controls the processes. / 197
A modern operating system has at least four duties: memory manager, process manager, device manager, and file manager.
Queue / A liner list in which data can only be inserted at one and, called the rear, and deleted from the other end, called the front. / 205
To handle multiple processes and jobs, the process manager uses queues.
Ready state / In process management, the state of processing in which the process is waiting to get the attention of the CPU. / 203
Where there is memory space available to load the program totally partially, the job moves to the ready state.
Real-time system / An operating system that is expected to do a tack within specific time constrains. / 196
A real-time system is expected to do a task within specific time constraint.
Reliability / The quality factor that addresses the confidence or trust in a system’s total operation. / 211
Design goals released by Microsoft are extensibility, portability, reliability, compatibility and performance.
Resource holding / A condition in which a process holds a resource but cannot use it until all other resources are available. / 207
Resource Holding isA process is currently holding at least one resource and requesting additional resources which are being held by other processes.
Running state / In process management, a state in which a process is using the CPU. / 203
The process scheduler chooses the processes or jobs to be executed only at the running state.
Scheduler / A program to move job from one state to another. / 204
Operating systemscheduling is the process of controlling and prioritizing messages sent to a processor. An internal operating system program, called the scheduler, performs this task.
Scheduling / Allocating the resourced of an operating system to different programs and deciding which program should use which resource, and when. / 196
A scheduling system allows one process to use the CPU while another is waiting for I/O, thereby making full use of otherwise lost CPU cycles.
Shell / A user interface in some operating systems, such as UNIX. / 197
Incomputing, ashellis auser interfacefor access to anoperating system's services.
Single-user operating system / An operating system in which only one program can be in memory at a time. / 196
When personal computers were introduced, there was a need for an operating system for this new type of computer. During this era, single-user operating system such as DOS was introduced.
Software / The application and system program necessary for computer hardware to accomplish a task. / 193
Computer software is divided into two broad categories: the operating system and application programs.
Starvation / A problem in the operation of an operating system in which processes cannot get access to the resources they need. / 207
Starvation is the opposite of deadlock.
State diagram / A diagram that shows the different states of a process. / 203
Every state diagram starts with an initial state, which is the state where the object is created.
Terminated state / In process management, a state in which a process has finished executing. / 204
A process may beterminated, either from the running state by completing its execution or by explicitly being killed. In either of these cases, the process moves to the terminated state.
Time sharing / Time-sharingis the sharing of a computing resource among many users by means ofmultiprogrammingandmulti-tasking. / 195
Multiprogramming brought the idea of time sharing: resources could be shared between different jobs, with each job bring allocated a portion of time to use a resource.
UNIX / A popular operating system among computer programmers and computer scientists. / 209
UNIX was originally developed in 1969 by Thomson and Ritchie of the Computer Science Research Group at Bell Laboratories.
User interface / A Program that accepts requests from users and interprets them for the rest of the operating system. / 197
Each operating system has a user interface, a program that accepts requests from users and interprets them for the rest of the operating system.
Utility / An application program in UNIX. / 210
A utility is a standard UNIX program that provides a support process for users.
Virtual memory / A form of memory organization that allows swapping of programs between memory and magnetic storage to give the impression of a larger main memory than really exists. / 202
The operating system manages virtual address spaces and the assignment of real memory to virtual memory.
Waiting state / A state in which a process is waiting to receive the attention of the CPU. / 203
Waiting states are a pure waste for a processor's performance.
Windows / Microsoft Windows(or simplyWindows) is a metafamily ofgraphicaloperating systemsdeveloped, marketed, and sold by Microsoft. It consists of several families of operating systems, each of which cater to a certain sector of the computing industry. / 211
Windows 1.0 was to compete withApple's operating system, but achieved little popularity.
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