Line number

Line numbers or line labels are used in QBasic as references to code lines. Numbers are required with GOTO and numbers or label names are required with GOSUB. Although not required in QBasic, other older programming languages such as GW Basic often required them. Line labels require a colon after them to differentiate them from keywords and variable names.

Microsoft's REMLINE.BAS program removes unnecessary line numbers

The following program can remove line numbers where they are not required by IF...THEN, GOTO, GOSUB, ERL, RUN or RESUME:

CLS REDIM linenumber(100000) PRINT "This Program removes unnecessary line numbers.": PRINT INPUT "Name of file: ", filename$: PRINT OPEN filename$ FOR INPUT AS #1 DO UNTIL EOF(1) LINE INPUT #1, a$ REM Get rid of quotes and REM statements. DO IF INSTR(a$, CHR$(34)) <> 0 THEN IF INSTR(INSTR(a$, CHR$(34)) + 1, a$, CHR$(34)) = 0 THEN EXIT DO: REM Mismatched quotes. Illegal code. a$ = MID$(a$, 1, INSTR(a$, CHR$(34)) - 1) + MID$(a$, INSTR(INSTR(a$, CHR$(34)) + 1, a$, CHR$(34)) + 1) ELSE EXIT DO END IF LOOP IF INSTR(UCASE$(a$), "REM ") <> 0 THEN a$ = MID$(a$, 1, INSTR(UCASE$(a$), "REM ")) IF INSTR(UCASE$(a$), "' ") <> 0 THEN a$ = MID$(a$, 1, INSTR(a$, "' ")) DO flag = 0 REM Break down compound statements and get line numbers. IF INSTR(a$, "GOTO ") <> 0 THEN flag = 1: n = INSTR(a$, "GOTO ") + 5: GOSUB tracknumber IF INSTR(a$, "GOSUB ") <> 0 THEN flag = 1: n = INSTR(a$, "GOSUB ") + 6: GOSUB tracknumber IF INSTR(a$, "THEN ") <> 0 THEN flag = 1: n = INSTR(a$, "THEN ") + 5: GOSUB tracknumber IF INSTR(a$, "ELSE ") <> 0 THEN flag = 1: n = INSTR(a$, "ELSE ") + 5: GOSUB tracknumber IF INSTR(a$, "RUN ") <> 0 THEN flag = 1: n = INSTR(a$, "RUN ") + 4: GOSUB tracknumber IF INSTR(a$, "RESUME ") <> 0 THEN flag = 1: n = INSTR(a$, "RESUME ") + 7: GOSUB tracknumber IF INSTR(a$, "RETURN ") <> 0 THEN flag = 1: n = INSTR(a$, "RETURN ") + 7: GOSUB tracknumber IF flag = 0 THEN EXIT DO ELSE a$ = MID$(a$, n) LOOP LOOP PRINT "Number of line-numbered statements kept:"; count CLOSE #1 OPEN filename$ FOR INPUT AS #1 OPEN "filename.tmp" FOR OUTPUT AS #2 DO UNTIL EOF(1) LINE INPUT #1, a$ flag = 0 IF VAL(MID$(a$, 1, 1)) <> 0 THEN FOR i = 1 TO count IF VAL(a$) = linenumber(i) THEN flag = 1: EXIT FOR NEXT IF flag = 0 THEN a$ = MID$(a$, INSTR(a$, " ") + 1) END IF PRINT #2, a$ LOOP CLOSE #1, #2 SHELL _DONTWAIT "notepad filename.tmp" PRINT PRINT "Back up original file as .org and give edited file original file name? [Y/N]" DO b$ = UCASE$(INKEY$) SELECT CASE b$ CASE CHR$(27): SYSTEM CASE "N" ON ERROR GOTO RESNXT KILL "filename.tmp" ON ERROR GOTO 0 PRINT PRINT "Temporary "+ CHR$(34) + "filename.tmp" + CHR$(34) + " was removed and no changes were made to original file." PRINT PRINT "Press any key to end." EXIT DO CASE "Y" ON ERROR GOTO resnxt KILL MID$(filename$, 1, INSTR(filename$, ".") - 1) + ".org" ON ERROR GOTO 0 NAME filename$ AS MID$(filename$, 1, INSTR(filename$, ".") - 1) + ".org" NAME "filename.tmp" AS filename$ PRINT : PRINT "File conversion completed. Press any key to end." EXIT DO END SELECT LOOP SLEEP SYSTEM tracknumber: DO count = count + 1 linenumber(count) = VAL(MID$(a$, n)) IF INSTR(a$, "ON") <> 0 AND INSTR(a$, "GOSUB") <> 0 OR INSTR(a$, "ON") <> 0 AND INSTR(a$, "GOTO") <> 0 THEN FOR i = n TO LEN(a$) IF VAL(MID$(a$, i, 1)) = 0 AND MID$(a$, i, 1) <> "0" AND MID$(a$, i, 1) <> "," AND MID$(a$, i, 1) <> " " THEN EXIT FOR IF MID$(a$, i, 2) = ", " THEN n = i + 1: EXIT FOR NEXT IF n <> i + 1 THEN EXIT DO ELSE EXIT DO END IF LOOP RETURN resnxt: RESUME NEXT

Code courtesy of Pete from the Network 54 Qbasic Forum

See also:

• GOTO , RUN
• GOSUB , RETURN
• RESUME, NEXT
• RESTORE
• IF...THEN

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