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