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Program Trace Routine
Tracing can be terminated in batch or demand mode with the following methods:
• Use the TOFF$ command (see 24.4.2). Program execution continues.
• Use the EXIT$ command (see 24.4.2)
24.3. Symbol Tables
When using SNOOPY, the u-field of the instruction is edited in octal if it does not refer to
control storage.
The calling program can provide a symbol table to SNOOPY using Fieldata characters
instead of octal values when the u-field falls within the address range of the program
being traced. To do this, store a value in the externally defined location SYMTB$.
SNOOPY uses the symbol table while tracing a program. The value stored in SYMTB$
has the following form:
0 17 18 35
nbr-of-entries table-addr
H1 H2
The symbol table at the specified address is an array of three-word entries in the form:
0 high +1 low
1 Fieldata symbol name or address of long name
2 bits symbol address
H1 H2
If the rightmost bit of bits (bit 17) is set, SNOOPY assumes word 1 of the entry is the
address of a 7- to 12-character Fieldata symbol instead of a 1- to 6-character Fieldata
symbol. This accommodates long labels.
The next word after the last entry may be another symbolic table descriptor word. This
occurs if bit 1 is set in the last entry of the symbol table. SNOOPY searches the symbol
table to which it points in the same fashion. This may be repeated to any level desired.
However, circularity must be avoided (in other words, pointing to the address of a
higher-level symbol table).
If the u-field of an instruction is between the low- and high-address values, edit the
u-field as the symbol given by the second word of the entry, plus or minus an offset
calculated from the symbol address in the third word. If the nbr-of-entries parameter of
SYMTB$ is zero as it is initially, all u-fields outside control storage are edited in octal
except TOFF$ and a number of ER indexes.
24–4 7833 1733–004