Why is the actual cycle of software development two or three times times longer than expected?

Heard of Beholder. This sentence in http://www.aliyun.com/zixun/aggregation/31.html "> The programmer's work also applies, in the end is why?" Matija The truth with a clever metaphor.

It's like driving back to the city center from the suburbs in the rush hour. The first 80% of the road is very smooth, high-speed well, maybe two hours to go, but to the city, they can not walk, traffic lights, sidewalks, all kinds of link and rookie drivers, may be two hours is not enough.

So is programming. You start by designing the framework, laying the groundwork for the whole project, and then starting to develop, a few weeks or months later, you're done with the whole project 80%, and the various key modules are starting to work.

But the show is just beginning, and when you're ready to polish the product, you'll find a lot of strange bugs popping up. For example: "Hey, do you know that this program crashes when you unplug the USB cable from the file?", "It appears that the program does not want to download a file with an exclamation point in the filename ..."

At this point, if the management orders to finish the remaining 20% as soon as possible, the development team will have to abandon the car, hiking over the last few obstacles, just to get to the location, leave the car that no matter. It may be possible to finish it on schedule, but it is unwise.

This article was posted to the HN, sparked a lively discussion of netizens, we have expressed empathy. A friend posted a wonderful question and answer about Quora: "Why is the real cycle of software development always two or three times times longer than expected?" The first answer is really witty and humorous.

Simply put, software development, like hiking, maybe you originally planned to walk 500 kilometers in 10 days, but really walk, you will find that the road encountered endless problems, every day to walk the mileage is decreasing, team morale is not very stable, postponed a lot of time is inevitable.

In fact, more than software development, to do any one of the products are most of the process. Hardware project is also to make prototype simple, real mass production will encounter a variety of problems, you need to withstand a resolution, sometimes also have to rework. The devil lurks in the details, and to achieve perfection, it takes extra effort to carve out the last 10% parts.