title: Why earlier versions of C made it mandatory to declare variables in the beginning?
body: <p>I have been going through a bit of history of C, and I find that in earlier versions of C, like in C89 standard, it is mandatory to declare variables at the beginning of a block. </p>
  
  <p>But I also find there are some relaxations from C99 standard specification, where variable can be declared anywhere before it is used.</p>
  
  <p>My question is why the earlier versions made it mandatory? my emphasis is to know if there was any technical difficulties in designing the compiler at those days, that prevented them identifying declarations at any point.</p>
  
  <p>Also, with a compiler design perspective I understand, with such a restriction in C89, it is easy to handle variable declarations and usage with the help of an intermediate file to store the mappings. But are there methods that can handle the case without using an intermediary file, say some memory based storage?.</p>