Converts a hexadecimal number to binary.
returns text representing a binary number, given hexadecimalnumber, which may be text, or a number (taken to be hexadecimal although it is not).
The binary number returned may have up to ten bits in two's complement representation; positive numbers are 0 to 111111111 (nine bits representing 0 to 511 decimal) and negative numbers 1111111111 to 1000000000 (ten bits representing -1 to -512 decimal).
hexadecimalnumber must therefore also lie in this range, and is given in two's complement form with up to ten digits.
numdigits is an optional number specifying the number of digits to return.
returns 11101 as text.
returns 10000 as text. The number 10 is read as hexadecimal.
returns 0010 as text. HEX2BIN adds leading zeroes to make 4 digits.
returns 1111111110 as text (twos complement representation of decimal -2).