Function is_printable_byte 

pub exec fn is_printable_byte(b: u8) -> bool

returns

matches!(
    b, b'A'..= b'Z' | b'a'..= b'z' | b'0'..= b'9' | b' ' | b'\'' | b'(' | b')' | b'+' |
    b',' | b'-' | b'.' | b'/' | b':' | b'=' | b'?'
),

Tests membership in PrintableString’s ASCII repertoire.