100 REM Binary search
110 CLS : REM  110 HOME for Applesoft BASIC : REM REMOVE for Minimal BASIC
120 DIM a(10)
130 LET n = 10
140 FOR j = 1 TO n
150 READ a(j)
160 NEXT j
170 REM Sorted data
180 DATA -31,0,1,2,2,4,65,83,99,782
190 LET x = 2
200 GOSUB 440
210 GOSUB 310
220 LET x = 5
230 GOSUB 440
240 GOSUB 310
250 GOTO 720
300 REM Print result
310 PRINT x;
320 IF i < 0 THEN 350
330 PRINT " is at index "; i; "."
340 RETURN
350 PRINT " is not found."
360 RETURN
400 REM Binary search algorithm
410 REM N - number of elements
420 REM X - searched element
430 REM Result: I - index of X
440 LET l = 0
450 LET h = n - 1
460 LET f = 0
470 LET m = l
480 IF l > h THEN 590
490 IF f <> 0 THEN 590
500 LET m = l + INT((h - l) / 2)
510 IF a(m) >= x THEN 540
520 LET l = m + 1
530 GOTO 480
540 IF a(m) <= x THEN 570
550 LET h = m - 1
560 GOTO 480
570 LET f = 1
580 GOTO 480
590 IF f = 0 THEN 700
600 LET i = m
610 RETURN
700 LET i = -1
710 RETURN
720 END