USER PROGRAM AREA INITIALIZATION
On
power-up. the user program area of memory
is
initialized to "+" charac-
ters (code 170) except for the first few beginning locations at 1024
on.
Location
1024
is
zero.
The initial link in locations 1025 and 1026
is
zero.
The pointers into
the user
area
are initialized
as
shown in Figure 6-4.
As
lines are entered and edited and
new
programs loaded, the contents
of memory locations throughout the user program area change.
They change.
however.
only
as
necessary for the current program. The user
area
is
not con-
tinuously reinitialized (to
"+"
or any other code). It
is
the pointers into the user
area
that determine the extents of the current program. if any. The action of a
NEW command
is
simply
to
readjust the pointers to the initial values shown in
Figure 6-4. A
CLR
does the same thing except that
it
adjusts the variable and array
pointers from the end of the program rather than the start of the program
as
NEW
does.
(In
fact.
if
vou have accidentally cleared the program
or
variables, vou
can reinstate them by "reading" through the user program area as needed
and
restoring the pointer values.)
315
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