最后的软件，也是最基础的软件，就是操作系统了，然而：
In using even these early machines, it clearly made no sense for each user to have to figure out independently how to interact with the computer.
为啥？确实没有操作系统（Operating System），但是有操作员（Operator）：
So although the earliest computers had no real operating system – that is, no soft�ware to control the operation of the entire computer system with anything like the sophistication we see today – it was still useful to collect together all the I/O subroutines – programs for input and output – and have them permanently loaded on the machine.
具体做法上：
In the earliest days of computers, users had to book a time slot on the machine, so graduate students were naturally allocated the nighttime slots!
This personalized system quickly evolved to a more efficient system in which the users were isolated from the machine by “operators.”
其实这是操作员（Operator）在排计划了（scheduling），是人工“操作系统”。
后来就有进化了—— 进化总是被不耐烦的、聪明人提出要求，这次是谁呢？人工智能之父麦卡锡（John McCarthy）：
McCarthy’s idea was that because the computer cycles from instruction to instruction very quickly on a human timescale, why not let the CPU switch from one memory area and program to another memory area and program every few cycles?
所谓的“分时”（time sharing）就出现了：
Time-sharing to me was one of these ideas that seemed quite inevitable. When I was first learning about computers, I [thought] that even if [time sharing] wasn’t the way it was already done, surely it must be what everybody had in mind to do.
沿着他的思想，随后出来的就是Multics (Multiplexed Information and Computing Service) 分时操作系统。
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