The operating system

VAX/VMS is a multiuser, multifunction virtual memory operating system that supports multiple languages, an interactive interface, and program development, tools. The operating system is designed for many applications, including scientific/time-critical, computational, time-sharing, data processing, transaction processing, and batch. The system performs demand paging, and under VAX/VMS a process pages only against itself – thus individual processes cannot significantly degrade the performance of other processes.

The memory management facilities provided by the operating system can be controlled by the user. Any program can prevent pages from being paged out of its working set. With sufficient privilege, it also can prevent the entire working set from being swapped out, to optimize program performance for time-critical or interactive environments. Sharing and protection are provided for individual 512-byte pages. As mentioned, four hierarchical access modes (kernel, executive, supervisor, and user) provide page protection.

VAX/VMS schedules CPU time and memory residency on a preemptive priority basis. Thus, time-critical processes do not have to complete with lower priority processes for scheduling services. Scheduling rotates among processes of the same priority. The scheduler adjusts the priorities of processes assigned one of the low 16 priorities to overlap I/O and computation. Time-critical processes can be placed in one of the top 16 scheduling priorities, in which case the scheduler does not alter their priority. Their priorities can be altered only by an appropriately privileged user.

The VAX/VMS command language is suitable for both the interactive and batch environments. Batch facilities under VAX/VMS include job

control, multistream spooled input and output, operator control, conditional command branching and accounting. Command procedures are supported by the command languages as a method of executing frequently used sequences of command, or creating new commands from the existing command set. Command procedures accept parameters and can include extensive control flow.

VAX/VMS provides a program development capability that includes editors, language processors, and a symbolic debugger. Its FORTRAN IV-PLUS and VAX-11 MACRO language processors produce native code The PDP-11 COBOL-74/VAX and PDP-11 BASIC-PLUS-2/VAX language processors produce compatibility mode code. Although compatibility mode and native mode cannot be freely mingled in a single program, compatibility mode jobs and native mode jobs can be run simultaneously, sharing system resources. Also, the two programs can share data and communicate through mailboxes.

VAX/VMS operating system provides a file and a record management facility that allows the user to create, access, and maintain data files and records within protected files. The record management services handle sequential and relative file organizations, sequential and random record access, and fixed- and variable-length records. Indexed files with sequential and random record access are available to compatibility mode programs, such as those written in PDP-11 COBOL-74/VAX or PDP-11 BASIC PLUS-2/VAX.

DECnet/VAX networking capabilities are optionally available for point-to-point interprocess communication, file access, and file transfer, and include down-line command file and RSX-11S system image loading; but these all require more explanation than can be provided here.

Notes:

transaction processing транзактная организация обработки

demand paging замещение страниц по требованию

facilities средства

page(out) откачка страниц

swap out откачка

management управление

working set рабочее пространство

sharing совместное пользование

kernel ядро

executive исполнитель

memory residence резидентная память

spooling подкачка

branching ветвление; переход

debugger отладчик; программа отладки

privilege приоритет

image изображение; фрагмент

relative реляционный

point-to-point двухпунктовый

scheduler планировщик

to rotate чередовать

VI. Запомните сочетания

under study изучаемый

under consideration рассматриваемый; обсуждаемый

under investigation исследуемый

under discussion обсуждаемый

under test испытываемый

under execution …

VII. Переведите предложения на русский язык, обращая внимание на выделенные слова

1. The machine under construction will be tested next month.

2. If the new product under consideration passes all the tests, it should be introduced.

3. The structure under discussion is very prominent in the outer segment.

4. The diode under test was cycled from 0 C° to 100 C° with a forward current of exactly 1 mA at 0 C°.

5. The instructions under consideration were written for the new installation.

5. Прочитайте текст

В абзацах 1, 3, 4, 6 выделите "цепочки" существительных, предложения, в которых они употребляются, переведите на русский язык.