Specifications

Using Callable System Routines
10.1 Deciding Which Routines to Use
10.1.2 Security Procedures
For security procedures, use system services to maintain rights database, to
use access control lists and process rights lists, to check access protection, and
to provide security erase patterns. To assign protection to a particular file, use
RMS.
10.1.3 File Management
For complex file manipulation, you would generally use RMS. RMS can create
complex file organizations; reorganize files; extend disk space for files; and get,
locate, insert, update, and delete records. There are RMS and RTL routines
for simple file manipulation such as opening, reading, deleting, renaming, and
closing files.
10.1.4 Memory Management
For memory management tasks, both RTL routines and system services can
acquire and free virtual memory. RTL memory management routines call system
services. RTL routines maintain a processwide pool of free pages that are
automatically reused. If you call system services directly, the program must keep
track of free pages. Direct calls to system services should be used when the size
requirements exceed 1000 pages for one request. RTL routines working with
such large requests may result in fragmenting the virtual address space. System
services give you more control because you can specify a specific virtual address
and unlock pages in memory.
10.1.5 Screen Management
For screen management, use RTL routines. The screen management routines
allow you to build terminal-independent screen management functions. They do
not rely on particular hardware devices; input is read from a virtual keyboard
and output is sent to a virtual display. With SMG$ routines, complex screens can
be built with several regions defined. The program can then work within a region
without regard to its position on the screen.
10.1.6 Math Operations Specific to OpenVMS
For math routines for OpenVMS systems, RTL routines can complete simple
arithmetic as well as the following functions:
• Exponentiation
• Complex exponentiation
• Complex function evaluation
• Floating-point trigonometric function evaluation
• Absolute value
• Numeric data conversions
10.1.7 Digital Portable Mathematics Library (AXP Only)
AXP
For math routines on AXP systems, the Digital Portable Mathematics Library
(DPML) provides a wide variety of mathematical routines including:
• Floating-point trigonometric function evaluation
• Exponentiation, logarithmic, power function evaluation
• Hyperbolic function evaluation
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