how to create Lookup table ?

A lookup table is just an array of constant data. You might pre-calculate data and use a static initializer, or perhaps you just allocate some RAM and execute an algorithm at init time to fill the array.

Here's an lame example that uses a lookup table to calculate the square roots of integers:

U16 sqrt[4] = { 0, 1000, 1414, 1732 };

U16 lameSqrt (U16 n)
{
return sqrt[n];
}

A lookup table is just an array of constant data. You might pre-calculate data and use a static initializer, or perhaps you just allocate some RAM and execute an algorithm at init time to fill the array.

Here's an lame example that uses a lookup table to calculate the square roots of integers:

U16 sqrt[4] = { 0, 1000, 1414, 1732 };

U16 lameSqrt (U16 n)
{
return sqrt[n];
}