Hand of Cards

Creating, Randomising and Dealing a Pack of Cards - Tutorial 014

This very clever algorithm by Alan Thomas, which I have here made more explicit, repays study to see how it works :

      REM: Hand of Cards
      REM: After Alan Thomas
      REM: Shows explicitly how the nos 1 TO 52
      REM: are converted to 4 suits of 13 cards
      REM: shuffled and dealt
      MODE8
      INPUTTAB(1,1)"How many cards : "n
      @%=6
      VDU14
      A$="diamondsclubs...hearts..spades.."
      DIM A(52)
      PRINT'"Unshuffled pack :"'
      REM: Show unshuffled pack
      FOR i=1 TO 52
        A(i)=i
        PRINTA(i);
        PROCdecode(A(i))
      NEXT i
      PRINT'"Shuffled Pack :"'
      REM: Shuffle the pack
      FOR j=52 TO 2 STEP -1
        r=RND(j)
        temp=A(r)
        A(r)=A(j)
        A(j)=temp
      NEXT j
      REM: Display shuffled pack
      FOR m=1 TO 52
        PRINTSTR$(m),A(m);
        PROCdecode(A(m))
      NEXT m
      PRINT'
      REM: Deal out n cards
      PRINT'"Here's your hand :"'
      FOR k=52 TO (53-n) STEP -1
        cardno=A(k)
        PROCdecode(cardno)
      NEXT k
      END
      :
      DEF PROCdecode(cardno)
      suit=cardno MOD 4
      facevalue=1 + (cardno MOD 13)
      PRINTfacevalue;SPC(2);" of ";
      PRINTMID$(A$,(8*suit)+1,8)
      ENDPROC

Annotated Listing

      REM: Hand of Cards
      REM: After Alan Thomas
      REM: Shows explicitly how the nos 1 TO 52
      REM: are converted to 4 suits of 13 cards
      REM: shuffled and dealt
      MODE8
      INPUTTAB(1,1)"How many cards : "n
      @%=6 *** Print formatting
      VDU14 *** Paged Mode on - press the shift key to make the screen scroll ***
      A$="diamondsclubs...hearts..spades.." ***** See penutimate line of the program to see how this is used ****
      DIM A(52) **** an Array of 52 memory locations to store the "numbers" of the cards (1 to 52)
      PRINT'"Unshuffled pack :"'
      REM: Show unshuffled pack
      FOR i=1 TO 52
        A(i)=i *** each card number is later converted into "1-13" of a suit - e.g. 13 is a King, 12 a Queen, 11 aJack
        PRINTA(i);
        PROCdecode(A(i)) *** converts the card's "number" eg 45 into a particular card"
      NEXT i
      PRINT'"Shuffled Pack :"'
      REM: Shuffle the pack
      FOR j=52 TO 2 STEP -1
        r=RND(j) *** This is the clever bit which does the shuffling ***
        temp=A(r)
        A(r)=A(j)
        A(j)=temp *** Can you see how it works? ***
      NEXT j
      REM: Display shuffled pack
      FOR m=1 TO 52
        PRINT STR$(m),A(m); ***STR$(m) converts the number m into a string which facilatates formatting ***
        PROCdecode(A(m))
      NEXT m
      PRINT'
      REM: Deal out n cards
      PRINT'"Here's your hand :"'
      FOR k=52 TO (53-n) STEP -1
        cardno=A(k)
        PROCdecode(cardno)
      NEXT k
      END
      :
      DEF PROCdecode(cardno) *** Look at the display when you run the program to see how this works out ***
      suit=cardno MOD 4 *** Rem 4 suits ***
      facevalue=1 + (cardno MOD 13) ***Rem 13 cards per suit ***
      PRINTfacevalue;SPC(2);" of ";
      PRINT MID$(A$,(8*suit)+1,8) *** The a part of the string, A$, starting ((8*suit)+1) letters along and 8 letters long ***
      ENDPROC

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