RESTORE

The RESTORE statement is not supported in Retro Rocket BASIC.

In BBC BASIC IV, RESTORE reset the pointer for READ so embedded DATA could be re-read.
Retro Rocket BASIC replaces this with file-based I/O.

Note: Use files to hold your constants and reopen them when you need to read again.; READ$ returns one character at a time, so build lines or tokens yourself if required.

Pattern 1: reopen to start reading again

values.txt

10
20
30

Program

DIM A,100
I = 0
LINE$ = ""
 
REM First pass: read all numbers
FH = OPENIN("values.txt")
WHILE NOT EOF(FH)
    C$ = READ$(FH)
    IF C$ = CHR(10) OR C$ = CHR(13) THEN
        IF LEN(LINE$) > 0 THEN
            I = I + 1
            A(I) = VAL(LINE$)
            LINE$ = ""
        ENDIF
    ELSE
        LINE$ = LINE$ + C$
    ENDIF
ENDWHILE
IF LEN(LINE$) > 0 THEN
    I = I + 1
    A(I) = VAL(LINE$)
ENDIF
CLOSE FH
 
REM Second pass: simply reopen and read again
FH = OPENIN("values.txt")
REM ... do another read as above ...
CLOSE FH

Pattern 2: cache once, reuse many times

Instead of re-reading the file, store values in an array on the first pass and reuse the array.

DIM A,100
COUNT = 0
 
REM Load once
FH = OPENIN("values.txt")
LINE$ = ""
WHILE NOT EOF(FH)
    C$ = READ$(FH)
    IF C$ = CHR(10) OR C$ = CHR(13) THEN
        IF LEN(LINE$) > 0 THEN
            COUNT = COUNT + 1
            A(COUNT) = VAL(LINE$)
            LINE$ = ""
        ENDIF
    ELSE
        LINE$ = LINE$ + C$
    ENDIF
ENDWHILE
IF LEN(LINE$) > 0 THEN
    COUNT = COUNT + 1
    A(COUNT) = VAL(LINE$)
ENDIF
CLOSE FH
 
REM Use many times without touching the file
SUM = 0
I = 1
WHILE I <= COUNT
    SUM = SUM + A(I)
    I = I + 1
ENDWHILE
PRINT "SUM = "; SUM

Tips

Store one value per line for simple parsing, or define your own separators and split by looking for those characters.
When you only need to go back to the start of a file, the simplest approach is close and reopen it.

See also:
OPENIN · OPENOUT · OPENUP · READ$ · EOF · VAL · LEN · CHR