cdc_6500_survival_guide
Differences
This shows you the differences between two versions of the page.
| Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
| cdc_6500_survival_guide [2021/03/15 23:23] – [File System] hc9 | cdc_6500_survival_guide [2021/03/15 23:29] – [File System] hc9 | ||
|---|---|---|---|
| Line 52: | Line 52: | ||
| * **Permanent files** | * **Permanent files** | ||
| * Permanent files are preserved by the system from their creation until their deletion by user command. Each permanent file is owned by a single user and is normally accessible only by its owner, though it is possible to make files accessible by other users as well. | * Permanent files are preserved by the system from their creation until their deletion by user command. Each permanent file is owned by a single user and is normally accessible only by its owner, though it is possible to make files accessible by other users as well. | ||
| - | + | | |
| - | | + | |
| * **Direct access** | * **Direct access** | ||
| * Used for random access and database applications. | * Used for random access and database applications. | ||
| - | |||
| * **Indirect access** | * **Indirect access** | ||
| * Common sequential access files, including program source files. | * Common sequential access files, including program source files. | ||
| Line 63: | Line 60: | ||
| * **Temporary files** | * **Temporary files** | ||
| * Whenever an indirect access file is accessed, or a new indirect access file created, the system first makes a temporary copy of the file, to which are directed all references and updates to the file. The temporary file must be saved in order for changes to be applied to the permanent file. Unsaved changes will be discarded at the end of the user's session. | * Whenever an indirect access file is accessed, or a new indirect access file created, the system first makes a temporary copy of the file, to which are directed all references and updates to the file. The temporary file must be saved in order for changes to be applied to the permanent file. Unsaved changes will be discarded at the end of the user's session. | ||
| - | + | | |
| - | | + | |
| * **Primary file** | * **Primary file** | ||
| * The primary file is the temporary file, usually a program source file, that a user is viewing, modifying, or executing at a given time. Although a user session may simultaneously open multiple temporary files, a given user may have only one primary file at a time. | * The primary file is the temporary file, usually a program source file, that a user is viewing, modifying, or executing at a given time. Although a user session may simultaneously open multiple temporary files, a given user may have only one primary file at a time. | ||
| - | |||
| * The currently selected primary file automatically determines the user's active subsystem. When a new indirect access file is saved as a permanent file for the first time, the file system records the active subsystem at the time. Then when the file is selected as primary sometime later, the system automatically activates the original subsystem. | * The currently selected primary file automatically determines the user's active subsystem. When a new indirect access file is saved as a permanent file for the first time, the file system records the active subsystem at the time. Then when the file is selected as primary sometime later, the system automatically activates the original subsystem. | ||
cdc_6500_survival_guide.txt · Last modified: 2022/12/05 06:33 by hc9