Technical data

SDA Description
Table SDA–8 (Cont.) SDA Operators
Operator Action
Binary Operators
/ Division
3
@ Arithmetic shifting
3
In division, SDA truncates the quotient to an integer, if necessary, and does not retain a remainder.
7.2.3 Precedence Operators
SDA uses parentheses as precedence operators. Expressions enclosed in
parentheses are evaluated first. SDA evaluates nested parenthetical expressions
from the innermost to the outermost pairs of parentheses.
7.2.4 Symbols
Names of symbols can contain from 1 to 31 alphanumeric characters and can
include the dollar sign ($) and underscore (_) characters. Symbols can take
values from –7FFFFFFF
16
to 7FFFFFFF
16
.
By default, SDA copies symbols into its symbol table from the files
SYS$SYSTEM:SYS.STB and SYS$SYSTEM:REQSYSDEF.STB. To add more
symbols to the symbol table, you can use the following SDA commands:
• READ—to add symbols from other symbol tables or object modules
• DEFINE—to create symbols and add them to the symbol table
In addition, SDA provides the symbols described in Table SDA–9.
Table SDA–9 SDA Symbols
Symbol Meaning
. (period) Current location
2P_CDDB Address of alternate CDDB for MSCP-served device
1
2P_UCB Address of alternate UCB for dual-pathed device
1
AMB Associated mailbox UCB pointer
1
AP Argument pointer
2
CDDB Address of class driver descriptor block for MSCP-served device
1
CLUSTRLOA Base address of loadable VAXcluster code
CRB Address of channel request block
1
DDB Address of device data block
1
DDT Address of driver dispatch table
1
1
The SHOW DEVICE command defines this symbol, if appropriate, to represent information pertinent
to the last displayed device unit. See the description of the SHOW DEVICE command for additional
information.
2
The value of those symbols representing the current SDA process context changes whenever you
issue a command that changes the context (see Section 4). These symbols include the general-purpose
registers (R0 through R11, AP, FP, PC, and SP); the per-process stack pointers (USP, SSP, KSP);
the page table base and length registers (P0BR, P0LR, P1BR, and P1LR); and the processor status
longword (PSL).
(continued on next page)
SDA–17