C Programming - Declarations and Initializations - Discussion

What is double ?

There are three types of constants:
1)Integer constants.
2)Real constants.
3)Char constants.

INTEGER CONSTANTS:
* It is have atleast one Digits.
* It must not have decimal point value.
* Normal unsigned value mentioned Positive

REAL CONSTANTS:
There are two types Real constants form:Fractional form, Exponential form.
Fractional Form:
* It is have at least one Digits.
* It must have decimal point value.
* Normal value mentioned Positive.
Exponential form: That constants should be used 'e' exponent.value declared before 'e' that is called "Mantissa".

CHAR CONSTANTS:
Char constants nothing but a single alphet,single digits,single symbols enclosed inverted commas. like 'A' or '1' or '='.
So Decimal value should be mentioned Real constants and then Float and Double are keywords of Real constants.

That question just only mentioned default real number so we using only float variable then why they used double. Just I need some more clarifications.

Friends I have one doubt, would you clarify?
in ANSI C,
The precedence order is !, ~, ++, --, +, -, *, (type) , sizeof.
But, in Let Us C,
The precedence order is -, ++, ~, !, &, *, (type) , sizeof.
What is the correct order?

Another doubt is.
In ANSI C, comma (,) operator associativity is left to right.
But in Let Us C, right to left.
What is the correct associativity?
Please tell me?

1. I need clarification where we use double and where we use float.

2. How data types are occupy the memory? If we gave int i=3 then it occupy the memory as 1 1 0 right or wrong and if we gave 3.2 how it will take.

@Nagchandra
We know how machine language gets work.Compiler can convert our all source codes to 0's & 1's. Float can occupy memory space:4 bytes. Double can occupy memory space:8 bytes. so, if we specify float a=1 or double b=1 it considered as 4bytes & 8bytes respec with same value as 1.0000etc. but if we specify float a=1.1,double b=1.1 the bit values for float and double may be unequal.so, it shows the result based on the condition.

void main()
{
float a=1.1;
double b=1.1;

if(a==b)
{
printf(" I love you\n");
}
else
{
printf(" I hate you\n");
}
}

Output: I hate you

void main()
{
float a=1;
double b=1;

if(a==b)
{
printf(" I love you\n");
}
else
{
printf(" I hate you\n");
}
}

Output: I love you

How this will happen if we consider var equalization?

Double variable have more precision.
for eg.,
6/36=0.166666666

So we can get more over approximate value

Hello Cheluvarajesh.

Double variable is always bigger than the Float variable whether the values are same.

Real number consists of both rational & irrational number.