I want to represent the result of a logical operation in decimal.

I thought that the 9OR3 in question was looking for a decimal representation of 9|3.
※ The bit operation for OR in C language is | and the bit operation for AND is &.

The idea is to convert numbers to binary numbers, perform &(AND) and |(OR) bit operations one bit at a time, and then convert the results to decimal numbers.
If you just want to know the answer, you can use printf to display the bit results as follows:

printf("%d\n", 15&7);

[Added]

The operator of the logical operation in C language is && and the OR is |.
The C language can treat integers as true or false values.
The true or false value of integer 0 is false, and any integer other than 0 is true.When evaluating, 1 or 2 is true, but the result is 1.
If any of the two integers is 0 (false), the logical AND (&) result is 0 (false), and if both integers are non-zero, the result is 1 (true).
If both integers are 0 (false), the logical OR (||) result is 0 (false), and the result is true (1) when at least one integer is non-zero.

Bit operations can be considered as logical operations for each bit.

"The question said ""I want to express it in decimal"", so I thought it was a bit operation and answered it without permission, but
" I added it to my answer because I thought it would be better to understand the difference between logical operation and bit operation.