在一个程序中通过修改参数实现三种调制方式，分别是AM、DSB和FM。
注释详细，适合初学者参考。-It s an analog modulation program by change a parameter.The three modulation types are AM, DSB, and FM. The program is easy to read and suitable for beginners.
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.001271s ]
SELECT `a`.`aid`,`a`.`title`,`a`.`create_time`,`m`.`username` FROM `jrk_downrecords` `a` INNER JOIN `jrk_member` `m` ON `a`.`uid`=`m`.`id` WHERE `a`.`status` = 1 GROUP BY `a`.`aid` ORDER BY `a`.`create_time` DESC LIMIT 10 [ RunTime:0.139261s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.001041s ]
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SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.000948s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.003223s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.000875s ]
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SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001195s ]
UPDATE `jrk_articles` SET `hits` = 2 WHERE `id` = 180414 [ RunTime:0.022971s ]
