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STANDARD OBJIECT PROGRAM FORMAT
Extended Symbol object programs are output by the assem-
bler as an object module. All object modules consist of an
ordered set of records. The Xerox loaders have the foci Ii ty
to load and link several object modules together to form
an executable program.
OBJECT MODULE RECORDS
Each object module record consi sts of two parts: a record
header and a record body.
1.
The record header contains record control information.
This information
is
in the first three words of each ob-
ject module record os follows:
[flU:::
ID
:=:r::)ec
ord s
ize~
C
S
Sequence
nt~rf{ber
Checksum----·
o
1
7 8
15
where
ID
is X'FF ' for all records except last, which
is X'9F'.
Record size
is the number of words (excluding
the three record control words) that com-
prise i·he active rec:ord. All words in excess
of the record size ore ignored.
1
~
record
size
~
51.
Sequence number
is, zero for the first record
of
th~
object module and increases by one
for each record thereafter. A load error wi
II
result if the records comprising an object
module are out of sequence.
If the" SOl bit
is set to
1,
the sequence number wi
II
be
ignored.
Checksum
is compu ted as the sum of the words
comprising the active record, not including
the record header. Carries of the most sig-
nificant bit are added to the low order bit.
If the "C" bit is set to 1, the checksum will
not be verified by the loader.
2.
The record body contai ns load items that control
and defi ne the load data.
LOAD ITEMS
Each load item consists of a header word folhwed by a
voriable number of load or control words.
The first load
item in an object module is a start-module item and the
last item (other than record padding) is an end-module
item.
Every load item header word has the same general format:
Bits 0-3
Type number.
4-7
Control i nformati on.
8-15
Number of load words or control words in
the load item. Thus, number plus
1
is al-
ways equal to the size of the load item.
Load item types are described in detail in the RBM/RT, BP
Reference tv\anual, 901037.
ASSEMBLER DIAGNOSTICS
Duri ng assembl y, the assembler checks the source program
for syntactical errors. If such errors are found, appropriate
flags are set and the assembly operation continues.
How-
ever, if an irrecoverable I/O error occurs, or if one of the
assembler tables is exceeded before an END line, the
assembly is aborted and an appropriate message is typed.
FLAGS
Flags indicate syntactical errors but do not cause the assem-
bly to terminate.
These flags appear at the left-hand mar-
gin of the assembly listing, preceding the instruction that
contains the error(s). One to three flags may be indicated
on one assembly listing line.
D
E
G
L
N
Q
R
S
T
Interpretati on
- - _ . - - -
Duplicate symbol definition or
reference.
Expression error or expression missing.
Address out of range.
Illegal operation code or illegal place
for a directive.
Label error (syntax or
$,$$
or AFNUM
used as a label).
Missing PEND directive line or END
or PEND directive in range of DO or
GOTO.
Procedure local string error.
The
relocatability of a procedure local
address string has changed, and the
output loader text is incorrect.
Relocatable expression error or illegal
use of a relocatable symbol.
Syntax error.
Significant digits lostdue to truncation.
Severity
- - - -
2
2
2
2
2
Standard Object Program Format/Assembler Diagnostics
57
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