first DATA statement at or after the given line number. (You can miss out the line number, in which case it is as though you had typed the line number of the first line in the program.)

Try this program:

10 READ a,b
20 PRINT a,b
30 RESTORE 10
40 READ x,y,z
50 PRINT x,y,z
60 DATA 1,2,3
70 STOP

In this program the data required by line 10 made a=1 and b=2. The RESTORE 10 instruction allowed x, y and z to be READ starting from the first number in the DATA statement. RUN this program again, without line 30 and see what happens.

Notes

You can store DATA statements in memory banks to take advantage of the expanded memory available on the ZX Spectrum Next. Refer to Chapter 23 – The Memory, for information on how to use BANK RESTORE to do this.

READ, DATA and RESTORE accept integer variables following the conventions set forth in Chapter 6 – Expressions.

DATA (function)

Apart from its use in subroutines as we saw in the previous chapter, DATA can also be used as a function that returns what the next DATA item to be read is; Return values can be: numeric (1), string (2) or none (0) – when there are no more data items available. This is most useful if we want to load a list of items with varying data types. Consider this example:

10 @rd:ON DATA:GO TO @prn:
   READ number: READ text$:
   ELSE GO TO @rd
20 GO TO @rd
30 @prn: PRINT text$;number
40 DATA 3,"Here we come KS"

What have we done here? We've used the handy ON...ELSE conditional selection structure and placed the DATA function in lieu of a variable argument since it returns one of 3 values. Then used the data type look ahead that DATA as a function provides to decide whether our next READ operation will be a numeric or string one (As ON expects its statements according to an increasing order of values, the exit condition is first).

Note that ELSE is really redundant here as there are 3 possible values of DATA and all are covered by the statements available, however it was put there as an additional demonstration of the complete ON...ELSE structure.