是的，这是一个无限循环。这是一个普通的，没有条件表达式循环。

从的为文档 ：

所有表达式for语句都是可选的;例如，下面的语句是用来写一个无限循环：

 为（;）
 {
 // ... 
} 
 

块引用>

I've been looking through some sample source code for an application I use and I came across this line:

for (;;)
{
// The rest of the application's code
}

It looks like this is to create an infinite loop, but I'm not familiar with ";;" and it's very hard to Google unfortunately.

Yes, that is an infinite loop. It's an ordinary for loop with no condition expression.

From the documentation for for:

All of the expressions of the for statement are optional; for example, the following statement is used to write an infinite loop:

for (; ; )
{
    // ...
}