The RESTORE statement is used to reset the DATA pointer to the beginning of the data.
- RESTORE [lineNumber|lineLabel]
- The line label or number enables a labeled data field to be READ more than once as required.
- Datafield label names are not required when working with ONE or a progression of data fields in the main body of code.
- Label multiple data fields to restore them to use them again when necessary.
- If RESTORE is used with unlabeled data fields or no datafield is designated then the first data field is read.
- Use RESTORE to avoid an "Out of Data" error when reading a data field!
- See the DATA statement for STRING data value specifications.
- Do not place DATA fields after SUB or FUNCTION procedures! QB64 will FAIL to RESTORE properly!
- QBasic allowed programmers to add DATA fields anywhere because the IDE separated the main code from other procedures.
Example 1: Restoring a labeled DATA field to avoid going past the end of DATA.
DO INPUT "Enter a month number(1 to 12): ", monthnum% RESTORE Months FOR i = 1 TO monthnum% READ month$, days% 'variables must match data field types NEXT PRINT "The month "; month$; " has"; days%; "days." LOOP UNTIL monthnum% < 1 OR monthnum% > 12 Months: DATA January, 31, February, 28, March, 31, April, 30, May, 31, June, 30 DATA July, 31, August, 31, September, 30, October, 31, November, 30, December, 31
Enter a month number(1 to 12): 6 The month June has 30 days.
- Note: String DATA values do not require quotes unless they have commas, end spaces or QBasic keywords in them.
Example 2: Using RESTORE to know the number of elements in the DATA in order to dimension and store the items in a array.
DO READ dummy$ 'we won't actually use this string for anything else than to know when there is no more DATA. count = count + 1 LOOP UNTIL dummy$ = "stop" 'when dummy$ = "stop" then we know that it is the last entry so it only does the above loop until then. count = count - 1 'since the last string is "stop" and we don't want to store it in the array. PRINT "The number of relevant entries are:"; count DIM entry$(count) 'Now we know how many elements we need to make space for (DIM) RESTORE 'We restore it so that it begins reading from the first DATA again. FOR c = 1 TO count READ entry$(c) 'read the DATA and store it into the array. NEXT 'we can now print the contents of the array: FOR c = 1 TO count PRINT entry$(c) NEXT END DATA "entry1", "entry2", "entry3", "stop"
The number of relevant entries are: 3 entry1 entry2 entry3
Note: Now we can add any number of entries without further compensation to the code.