为什么旧的C语言规范要求预先声明函数-本地变量?

In the C programming language, all of the language revisions I have worked with enforced up-front variable declarations before any non-declarative/assignative expressions would be evaluated. C++ seems to have waived this requirement from all versions. I also recognize more modern version of C have waived this requirement as well, but I have yet to use any of those standards. In the C programming language, all of the langu