var result = 1.0 + 2.0;     // result === 3.0 returns true

var result = 0.1 + 0.2;     // result === 0.3 returns false

function strip(number) {
    return (parseFloat(number.toPrecision(12)));
}

public static string BinaryRepresentation(double value)
{
    long valueInLongType = BitConverter.DoubleToInt64Bits(value);
    string bits = Convert.ToString(valueInLongType, 2);
    string leadingZeros = new string('0', 64 - bits.Length);
    string binaryRepresentation = leadingZeros + bits;

    string sign = binaryRepresentation[0].ToString();
    string exponent = binaryRepresentation.Substring(1, 11);
    string mantissa = binaryRepresentation.Substring(12);

    return string.Format("{0}:{1}:{2}", sign, exponent, mantissa);
}

0.1 => 0:01111111011:1001100110011001100110011001100110011001100110011010
0.2 => 0:01111111100:1001100110011001100110011001100110011001100110011010

0.1 = 2^-4 * [1].1001100110011001100110011001100110011001100110011010
0.2 = 2^-3 * [1].1001100110011001100110011001100110011001100110011010

0.1 = 2^-3 *  0.1100110011001100110011001100110011001100110011001101(0)
0.2 = 2^-3 *  1.1001100110011001100110011001100110011001100110011010
sum = 2^-3 * 10.0110011001100110011001100110011001100110011001100111

sum = 2^-2 * 1.0011001100110011001100110011001100110011001100110011(1)

a = 2^-2 * 1.0011001100110011001100110011001100110011001100110011
x = 2^-2 * 1.0011001100110011001100110011001100110011001100110011(1)
b = 2^-2 * 1.0011001100110011001100110011001100110011001100110100

sum = 2^-2 * 1.0011001100110011001100110011001100110011001100110100

0.1 + 0.2 => 0:01111111101:0011001100110011001100110011001100110011001100110[100]
0.3       => 0:01111111101:0011001100110011001100110011001100110011001100110[011]

0.1 + 0.2 => 0.300000000000000044408920985006...
0.3       => 0.299999999999999988897769753748...

function add(a, b, precision) {
    var x = Math.pow(10, precision || 2);
    return (Math.round(a * x) + Math.round(b * x)) / x;
}

function getFloat(int) {
    var num = new Number(int);
    return parseFloat(num.toPrecision(2));
}

if( (n * 0.1) < 100.0 ) { return n * 0.1 - 0.000000000000001 ;}
                    else { return n * 0.1 + 0.000000000000001 ;}

0.1 + 0.2 = 0.30000000000000004
0.1 + 0.7 = 0.7999999999999999
...
1.7 + 1.9 = 3.5999999999999996
1.7 + 2.2 = 3.9000000000000004
...
3.2 + 3.6 = 6.800000000000001
3.2 + 4.4 = 7.6000000000000005

0.6 - 0.2 = 0.39999999999999997
0.5 - 0.4 = 0.09999999999999998
...
2.1 - 0.2 = 1.9000000000000001
2.0 - 1.9 = 0.10000000000000009
...
100 - 99.9 = 0.09999999999999432
100 - 99.8 = 0.20000000000000284

>>> 0.1 + 0.2 == 0.3
False
>>> Decimal('0.1') + Decimal('0.2') == Decimal('0.3')
True

SIGN EXPONENT FRACTION

#include <stdio.h>
#include <limits.h>

void
xx(float *x)
{
    unsigned char i = sizeof(*x)*CHAR_BIT-1;
    do {
        switch (i) {
        case 31:
             printf("sign:");
             break;
        case 30:
             printf("exponent:");
             break;
        case 23:
             printf("fraction:");
             break;

        }
        char b=(*(unsigned long long*)x&((unsigned long long)1<<i))!=0;
        printf("%d ", b);
    } while (i--);
    printf("n");
}

void
yy(float a)
{
    int sign=!(*(unsigned long long*)&a&((unsigned long long)1<<31));
    int fraction = ((1<<23)-1)&(*(int*)&a);
    int exponent = (255&((*(int*)&a)>>23))-127;

    printf(sign?"positive" " ( 1+":"negative" " ( 1+");
    unsigned int i = 1<<22;
    unsigned int j = 1;
    do {
        char b=(fraction&i)!=0;
        b&&(printf("1/(%d) %c", 1<<j, (fraction&(i-1))?'+':')' ), 0);
    } while (j++, i>>=1);

    printf("*2^%d", exponent);
    printf("n");
}

void
main()
{
    float x=-3.14;
    float y=999999999;
    printf("%lun", sizeof(x));
    xx(&x);
    xx(&y);
    yy(x);
    yy(y);
}

-- .../terra1/stub
@ qemacs f.c
-- .../terra1/stub
@ gcc f.c
-- .../terra1/stub
@ ./a.out
sign:1 exponent:1 0 0 0 0 0 0 fraction:0 1 0 0 1 0 0 0 1 1 1 1 0 1 0 1 1 1 0 0 0 0 1 1
sign:0 exponent:1 0 0 1 1 1 0 fraction:0 1 1 0 1 1 1 0 0 1 1 0 1 0 1 1 0 0 1 0 1 0 0 0
negative ( 1+1/(2) +1/(16) +1/(256) +1/(512) +1/(1024) +1/(2048) +1/(8192) +1/(32768) +1/(65536) +1/(131072) +1/(4194304) +1/(8388608) )*2^1
positive ( 1+1/(2) +1/(4) +1/(16) +1/(32) +1/(64) +1/(512) +1/(1024) +1/(4096) +1/(16384) +1/(32768) +1/(262144) +1/(1048576) )*2^29
-- .../terra1/stub
@ bc
scale=15
( 1+1/(2) +1/(4) +1/(16) +1/(32) +1/(64) +1/(512) +1/(1024) +1/(4096) +1/(16384) +1/(32768) +1/(262144) +1/(1048576) )*2^29
999999999.999999446351872

999999999.999999446351872

<?php
    $a = 1.23456789;
    $b = 1.23456780;
    $epsilon = 0.00001;

    if(abs($a-$b) < $epsilon) {
        echo "true";
    }

var foo = 0.1;
var bar = 0.2;
function add(foo, bar, precision){
    return parseFloat((foo + bar).toFixed(precision));
}

var result = myBinaryFunction (); // The result contains **0.06999999999999999**
    myBinaryFunction (){
        var x = 0.01 + 0.06;
        return x;
    }

var result = myParsedFunction() // The result contains 0.07
    function myParsedFunction() {
        var x = parseFloat(0.01) + parseFloat(0.06);
        return x.toFixed(2);
    }