Confusing Chr$ explanation

[SagaraS]

A simple ASCII Table.
ESC - End Program
Arrow keys to select the character

Code: (Select All)

' instructs the compiler to require variable declaration

OPTION _EXPLICIT



' Control function off to set all characters

_CONTROLCHR OFF



' dimension variables

DIM winX AS _UNSIGNED INTEGER

DIM winY AS _UNSIGNED INTEGER

DIM i AS _UNSIGNED _BYTE

DIM x AS _UNSIGNED _BYTE

DIM y AS _UNSIGNED _BYTE

DIM selx AS _UNSIGNED _BYTE

DIM sely AS _UNSIGNED _BYTE

DIM keyin AS STRING



' Create window area with colors

COLOR 4, 7

winX = 14

winY = 4

FOR y = winY + 0 TO winY + 16

  FOR x = winX + 0 TO winX + 16 * 3

    LOCATE y, x: PRINT SPACE$(2);

  NEXT x

NEXT y



' Create table info

FOR i = 0 TO 15

  LOCATE winY, winX + (i * 3) + 3: PRINT "0" + HEX$(i);

  LOCATE winY + i + 1, winX: PRINT HEX$(i) + "0";

NEXT i



' Create ASCII characters

' Init values for the table of ASCII chars

COLOR 0, 7

winX = winX + 1

winY = winY + 1



DO

  ' Output of all ASCII characters in the table

  x = 0

  y = winY

  FOR i = 0 TO 255

    IF selx = x AND sely = y - winY THEN COLOR 7, 2 ELSE COLOR 0, 7

    LOCATE y, winX + (x * 3) + 3: PRINT CHR$(i);

    x = x + 1

    IF x = 16 THEN

      x = 0

      y = y + 1

    END IF

  NEXT i



  ' Output of decimal and hex value of current char

  COLOR 0, 7

  LOCATE winY + 16, winX - 1: PRINT SPACE$(25);

  LOCATE winY + 16, winX - 1: PRINT "ASCII:  DEC(" + LTRIM$(STR$(sely * 16 + selx)) + ")  HEX(" + HEX$(sely * 16 + selx) + ")";



  ' Key Input

  DO

    keyin = INKEY$

  LOOP WHILE keyin = ""



  ' Arrow keys to select the current char

  IF keyin = CHR$(0) + CHR$(77) THEN IF selx >= 15 THEN selx = 0 ELSE selx = selx + 1

  IF keyin = CHR$(0) + CHR$(75) THEN IF selx <= 0 THEN selx = 15 ELSE selx = selx - 1

  IF keyin = CHR$(0) + CHR$(80) THEN IF sely >= 15 THEN sely = 0 ELSE sely = sely + 1

  IF keyin = CHR$(0) + CHR$(72) THEN IF sely <= 0 THEN sely = 15 ELSE sely = sely - 1



  ' ESC to end the program

LOOP WHILE keyin <> CHR$(27)