本算法与书上的相比稍微改动了一些。

因为日常加密中，明文不单是数字，经常会有字母或者其他字符出现。

本程序的思想就是先把明文以字符形式读取，转化成ASCII码，再把ASCII码转化成数字形式。

因为ASCII码共有256个也就是2的8次方，占8位二进制，把这八位二进制分为两部分，每部分占4位进行加密。

加密的算法和书上类似，先用密钥选取表，行，取反，然后与明文做异或，移位等运算。

最后得出两个4位的二进制数，合为一个，转化成十进制形式存储为密文。-The algorithm is compared with a little book on a number of changes. Because of the daily encryption, the plaintext is not only a number, often have letters or other characters appear. This is the first clear thought process to form characters read into ASCII code, ASCII code then converted into digital form. ASCII code for a total of 256 is 2 to the 8th power, accounting for 8-bit binary, this binary consists of two eight parts, each accounting for 4-bit encryption. Encryption algorithm and a similar book, first select the table with the keys, rows, inverted, and then XOR with the plaintext to do, shift and other operations. Came to the conclusion of two 4-bit binary number, into one, converted to decimal form of storage for the ciphertext.