Codes in binary system BCD codes: for decimal digit Gray code: for numbers in binary system; AsCIi code: for characters ey point Use n bits. we can make 2n different words: To make n code-words. you must use logn bits
多元函数 定义 11.2.1 设 D 是 n R 上的点集,D 到 R 的映射 f : D →R, x 6 z 称为 n 元函数,记为 = fz x)( 。这时,D 称为 f 的定义域, f D)( = ∈ R = fzz xx ∈ D}),(|{ 称为 f 的值域,Γ= }),(|),{( 1 R ∈=∈ D + x fzz xx n 称 为 f 的图象
Modular arithmetic – Used to define a finite field – a = b mod n means that if a and b are divided by n they produce the same remainder – a*b mod n can result in 0 even if a and b are not 0