下面的实例可以回答你的问题:
We do something using a computer. / We do something by computer. 我们用计算机做某事。
He ran a program on a computer. 他用计算机编出一个程序。
The entire process is done by computer. 整个过程由计算机操纵。
The missile was automatically launched by the computer. 这枚导弹是通过计算机自动发射的。
Is the information available on the computer? 计算机内有该信息吗?
(以上摘自席玉虎主编《英语常用词用法详解大词典》p.761)
All our customer orders are handled by computer. 我们所有顾客的订单都是用电脑来处理的。
We've put all our records on computer. 我们把自己所有的纪录都输入了电脑。
on a computer 在计算机上
by computer 用计算机
(以上摘自《剑桥高阶英汉双解词典》p.436)
He works all day on / with a computer. (《韦氏高阶英语词典》p.332)