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Samuel Gomes edited this page Nov 8, 2022 · 1 revision

The MOD operator gives the remainder after division of one number by another (sometimes called modulus).

Syntax

remainder = numerator MOD divisor

Parameter(s)

Description

  • Floating decimal point numerator and divisor values are CINT rounded (e.g. 19 MOD 6.7 returns 5 just like 19 MOD 7 would).
  • MOD returns 0 if a number is evenly divisible by integer division ( []() ) or the number divided is 0.
  • divisor (second value) must not be between 0 and .5. This will create a ERROR Codes due to CINT rounding the value to 0.
  • The result has the same sign as the numerator (e.g. -1 MOD 7 returns -1, not 6).
  • Division and multiplication operations are performed before addition and subtraction in QBasic's order of operations.

Example(s)

  I% = 100 \ 9 
  R% = 100 MOD 9
  PRINT "Integer division ="; I%, "Remainder ="; R% 


  Integer division = 11        Remainder = 1

Explanation: Integer division 100 \ 9 returns 11. 11 * 9 = 99. So the remainder must be 1 as 100 - 99 = 1. Normal decimal point division would return 11.11111.

Comparing normal, integer and remainder division.

tmp1$ = " Normal:         ####.# / #### = ##.###   "
tmp2$ = " Integer:        ####.# \ #### = ###      "
tmp3$ = " Remainder:    ####.# MOD #### = ####     "
FOR i = 1 TO 6
   SELECT CASE i
     CASE 1: numerator = 1: divisor = 5
     CASE 2: numerator = 13: divisor = 10
     CASE 3: numerator = 990: divisor = 100
     CASE 4: numerator = 1100: divisor = 100
     CASE 5: numerator = 4501: divisor = 1000
     CASE 6: numerator = 50.6: divisor = 10
   END SELECT
LOCATE 5, 20: PRINT USING tmp1$; numerator; divisor; numerator / divisor
LOCATE 7, 20: PRINT USING tmp2$; numerator; divisor; numerator \ divisor
LOCATE 9, 20: PRINT USING tmp3$; numerator; divisor; numerator MOD divisor
DO: SLEEP: LOOP UNTIL INKEY$ <> ""                              
NEXT

Integer division and MOD can be used to convert values to different base numbering systems from base 2 to 36 as STRING:

CLS
DO
  INPUT "Enter a base number system 2 to 36: ", b%
  IF b% < 2 OR b% > 36 THEN EXIT DO
  PRINT "Enter a positive value to convert: ";
  num$ = ""
  DO: K$ = INKEY$
    num$ = num$ + K$
    LOCATE CSRLIN, POS(0): PRINT K$;
  LOOP UNTIL K$ = CHR$(13)
  n& = VAL(num$)
  IF n& = 0 THEN EXIT DO
  Bnum$ = BASEN$(n&, b%)
  PRINT Bnum$ ', VAL("&H" + Bnum$) 'tests hexadecimal base 16 only
LOOP

END

FUNCTION BASEN$ (number&, basenum%)
IF basenum% < 2 OR basenum% > 36 OR number& = 0 THEN EXIT FUNCTION
num& = number& 'protect value of number!
DO
  remain% = ABS(num&) MOD basenum% ' remainder is used to create actual digit 0 to Z
  num& = num& \ basenum% ' move up one exponent of base% with integer division
  IF remain% > 9 THEN
    b$ = CHR$(65 + (remain% - 10)) 'limited to base 36
  ELSE: b$ = LTRIM$(STR$(remain%)) ' make remainder a string number
  END IF
  BN$ = b$ + BN$ ' add remainder character to base number string
LOOP UNTIL num& = 0
BASEN$ = BN$
END FUNCTION

Note: Base numbering systems over base 10(0 - 9) use alphabetical letters to represent digits greater than 9 like &H(0 - F).

See Also

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