How to convert certain bits in a number?

Question

Programming

I do not understand how to convert the given bits in a number that is not known in advance.
For example, the number 115 in binary form is 1110011.
We want to make 3 bits to the left of the second position as ones.
To do this, we must apply the OR operation: res = 1110011 | 0011100
But if the number itself, position and number of bits are set dynamically, how to select numbers?

Answer 1

If the position number is pos, the number of digits is len, and the number to be changed is x, then the answer is
x | (((1 << len) - 1) << pos)

Answer 2

Generate numbers that correspond to the desired ones in the binary system.
For example, to set 1 to the nth digit of a number, you can use shift:
a = 1 << n;

Answer 3

You can take a unit (var1 = 00000001), apply | (bitwise or), then we get 1 in the first bit, bitwise left shift to var1 - we get (00000010) and also apply | to the correct number.
Very good article:
chipenable.ru/index.php/programming-avr/item/4-uch...