I'm sure DASH can divide and multiply absolutely fine. It has * and /.

I noticed, but the way you're doing it is perhaps the hardest possible way. If you just keep your number as an integer, you can calculate it as an integer, because it is an integer. Addition and subtraction work completely straight. Multiplication and division will need correction before and afterwards respectively. And you will have to stay away from the integer limit because the result of multiplying 64-bit MAXINT by 64-bit MAXINT is a 128-bit number.

Anyway, you can use a here-document to feed values into read. There's another, older trick though, which works especially well in functions and should work anywhere.

Code:

DP=3
MOD=1000

function readnum {
        OLDIFS="$IFS"
        IFS="."
                set -- $1 # Set $1, $2, etc, splitting on "."
        IFS="$OLDIFS"

        N=$1
        FRAC=$2

        [ "$N" = "0" ] && N=""

        for((X=0; X<DP; X++))
        do
                D="${FRAC:$X:1}"
                [ -z "$D" ] && D="0"
                N="$N$D" # Prepend digits to N
        done
}

readnum "0.5"

echo "Integer $N is fixed point $((N/MOD)).$((N%MOD))"