System Tapes
General
Make-up
of
the
Compiler
Tape
General
Make-up
of
the
Subroutine
Tape
68
The
sections of
the
object deck, identified
by
card
number, are as follows:
Card
N
um
bers
0001
through
0008
0009
through
0054
0055
through
last
card
Loading
routine
and
add
tables
Program
loader
Compiled
instructions
Communication
card
Symbol
table
Relocated subroutines
and
arithmetic
and
input/
output
subroutines,
when
required.
NOTE:
When
the
symbol
table
is loaded, only constants
and
statement
numbers
are
placed
into
the
data
tables.
Variables
computed
in a
FORTRAN
object
program
are stored in specific 10-digit
fields
in
core storage,
the
addresses of
which
have
been
determined
in
the
com-
pilation process. Addresses are assigned in descending order from
the
highest-
numbered
storage location,
in
the
order
in which
the
variables, constants,
and
statement numbers
are
encountered
in
the
source program.
The
order
of address
assignment
is
repeated
for
each
object
program
compiled.
The
values
computed
and
stored
during
the
execution of an object program are
not
disturbed
by
the
loading of
another
object program,
if
the
variables have
appeared
in
the
second
source program in exactly
the
same
order
as
in
the
first. By this means, for example,
if
an array of variables is
computed
in
an
object program, another object
program
may
be
loaded
immediately to use
the
same
computed
values in further computa-
tions.
The
names of
the
variables
used
in
this
way
need
not
be
the
same from one
source program to another.
An involved algebraic calculation
might
require
the
use of temporary storage
fields which
are
automatically assigned
by
the
compiler.
For
this reason, variables
appearing
in
the
same order,
but
which
are
defined for the first time
in
the
body
of different source programs
may
not
be
given
the
same assigned address. Symbol
table listings
at
compilation time will disclose any such lack of correspondence.
The
compiler
tape
consists of two programs
separated
by
a group of records
which
are
processed
when
the
tape
isread
into
the
1620.
The
first
program
is
the
initialization
phase
which reads in
the
first five records on
the
tape
following
the
program itself,
and
punches
them
out
into
the
object tape. This
program
then
initializes
the
symbol table area
and
the
area into which source statements will
be
read. Finally, a record containing
the
number
of
the
subroutines
included
and
individual records containing
the
names of
the
subroutines are
read
in
and
processed.
The
rest
of
the
tape
which
contains
the
compiler
is
then
read
in
and
a
halt
instruction is executed.
The
starting instruction for each
program
is
in
location
00402.
During
compilation, after
each
statement
is
processed,
the
pro-
gram returns to location
00462 to continue.
The
first section in
the
subroutine
tape
is a loading routine which causes
the
subroutine relocator program which follows
it
to
be
read
and
executed.
The
relocator processes
the
relocatable subroutines which immediately follow
it
on
the
tape,
and
finally reads in
and
processes
the
arithmetic
and
input/output
sub-
routines
which
are
contained in
the
last record
on
the
tape.
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