The best one I used before was a phrase input method made by someone in Harbin. It hooked onto other Chinese character support systems. Unfortunately it was a trial version and could only be used on disk. It was 100 times better than Microsoft Pinyin.
I searched online for the author Wang Xiaolong and found this passage:
The earliest origins can be traced back to HIT in the late 1980s. At that time, Wang Xiaolong, then a doctoral student there, carried out research on Chinese word segmentation, applied for an 863 project, and wrote a paper on "the minimum segmentation problem and its solution." After that, Wang Xiaolong developed the InSun input method, a whole-sentence-based input system. In the early 1990s it was only used for demonstrations and achievement exhibitions and the like. I heard it was occasionally sold to some Japanese companies for use in certain special-purpose typewriters, and then there was no news of it for many years. In the mid-1990s it was sold to Microsoft for 100,000 US dollars, which of course was a pretty good price. And so, starting from the Chinese edition of Windows 95, there was the "Microsoft Pinyin Input Method" everyone saw. Although it has many critics, Microsoft used similar methods to get Intelligent ABC as well and "distributed" it free to Chinese users. But this "free" was only formal; in reality, the cost had already been calculated into the Windows operating system and was ultimately still paid by the users. The result was misery for input-method developers and manufacturers.
Even the pinyin input method provided by Microsoft is not necessarily easy to use. Someone once mocked it by saying the input method is like having a cold and wiping your nose: logically, once you have a little snot, you should quickly wipe it away instead of waiting until it gets long and drops onto your mouth before dealing with it. But Microsoft Pinyin doesn't do that. It lets you type a long stretch and then go back to revise it. Since the intelligence level is not high, the mistakes are baffling. If you're typing from a manuscript, it's easier to find the errors. But if you're typing as you think, you may even forget which words you were supposed to choose.
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Actually InSun isn't as troublesome as Microsoft Pinyin.