Sharp PC-1500A Instruction Manual page 137

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C.1. Fixed Memory Area
Although all variables of the same type are utilized in the same manner. they are not treated
the same internally. The
PC·
1500A includes a
"fixed
memory"
area with enough storage space
for 26 numeric variables and 26 character string variables (string size of 16 characters). Con·
sequently the variables A throu1)h Z, and the variables AS through ZS are permanently allocated
within this area.
All other variables, ir,cluding those \vith
t\VO
character names, are allocated within the main
memory area of the co1l'lputcr. Th is main memory area is also shared by the instructions of t.he
program. alth ough the variables are allocated beginning at the opposite end of memory from the
instructions. Becaus.e the program instructions and data share the same area
it
is possible for the1n
to use up all available
stor~ .
In this case an ERROR in the range 177 through 181 will occur.
It
is important to
reali2e
that
the
two
memory areas arc
not treated the
same
upon
program
initiation. This is
explained
in the chart in the
next
section. Basically, variables in
the
fixed
memory area are never cleored
except
by an explicit CLEAR statement.
Those
in main memory
arc cleared whenever a program is begun 1;.•1ith
the AUN
command.
One other idiosyncrasy about the fixed memory aroa is that the data in this urtta nlay be
redefi ned as an array whoso name is@ (At Sign). for numeric variables. and @S for string variabl cs.
Thus. t he designation @(11 is the same storage location as the variable A and@ (26) is the same
storage location as the variable Z. The designation @S (5) refers to the same location as ES, and
the designation @S (20) refers to the same location as TS. For o bvious re3$ons subscripts above 26
arc not allowed. Notice that the arrays@ and @Sneed no t
be
d imensioned before use.
C.2. COMPARISON CHART OF PROGRAM
INITIATION M ETHODS
RUN GOTO DEF
Display is cleared.
y
y
N
Cursor returns to first c· o l umn.
y
N
N
WAI T interval is set to infin ite . N
N
N
Trace mode is al tcrcd.
N N
N
Fixed Memory Area is cleared. N
N
N
Main Memory Area is cleared.
y
N
N
FOR·NEXT. GOSUB
y y
y
internal stack is cleared.
ON ERROR GOTO is
y
N N
cancelled.
DATA pointer fo r READ
y
N
N
operation is RESTOREd .
US I NG format is cane-0lled.
y
N
N
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