Try to solve the problem of the exam in computer science.?

Question

IT education

Actually a problem.
For the transmission of noise-immune messages in the alphabet, which contains 16 different characters, a uniform binary code is used. This code satisfies the following property: any code word contains an even number of ones (possibly none). What is the smallest length of a code word?
word by word.
The semantic wording is missing for me. And then it became interesting, do I have one?

Answer 1

5
1 (even 1 / 0) + 4 per character
Example:
0 - 00000
1 - 10001
2 - 10010
3- 00011
...
15 - 01111