[ori_b]

> you must trace the entire system

No, just the part you care about. You do need a high level mental model of the system. I've never seen a system where this is not the case, regardless of the number of comments. Even literate programming -- or at least, the examples of it that I've seen -- suffered from this. (Amusingly, I found literate programming examples were often easier to understand by mostly ignoring the prose and looking at the code.)

[flatline3]

> You do need a high level mental model of the system.

That is extremely time-consuming to build without code comments and documentation, regardless of how "literate" the code is, because code alone can not express sufficiently detailed invariants, and simple logical/atomic operations involve a non-trivial amounts of code. (especially when writing in C).

There's almost nothing I hate more than inheriting a complex uncommented code base and spending hours or days tracing out the code to build a high-level mental model, when instead, with reasonable comments, I could have had that model nearly immediately.

[ori_b]

You want some sort of design document. Comments are not sufficient to describe the way that the concepts interconnect. They are almost always detail oriented, scattered and do not give the big picture.

Comments embedded in source code are singularly unsuited to giving the sort of interconnection of concepts that allows you to quickly and efficiently understand build a model of the system. They are a poor substitute for real documentation.

Something like this should always be present to describe the overarching structure of the system: ftp://gcc.gnu.org/pub/gcc/summit/2003/GENERIC%20and%20GIMPLE.pdf http://gcc.gnu.org/onlinedocs/gccint/RTL.html

Incidentally, I'm not sure if you're familiar with literate programming. That's where the code is almost an afterthought to the comments. This is an example of a literate program: http://tug.org/texlive/devsrc/Build/source/texk/web2c/tex.we.... You may be familiar with it -- it's tex, the core engine used by LaTeX. Compiled to PDF, the source looks like this: http://eigenstate.org/tmp/tex.pdf.

[flatline3]

Design documents are necessary, but are no replacement for comments. When working in GCC briefly, I found the design documents to not be nearly so valuable as the (few, poor) comments that existed in the code (objc).

[dahvyd]

The problem with comments is that they decay into irrelevance and worse, lies (that chapter of Clean Code will live with me forever). You can't write a unit test to ensure comment correctness, but you can for code correctness. Hence the code is the only reliable source of the truth.

[flatline3]

Comments only decay into irrelevance if lazy developers don't do their job. Circularly, it's developers that don't write comments that claim comments decay into irrelevance.

Imagine that.

[einhverfr]

However, for maintenance programmers to do their job, if the comments mostly describe the code, they have to ignore the comments. Why make the maintenance programmer's job any worse?

Good comments are golden, but bad comments (those that tell you what the code is doing or duplicate coding logic in the comments) are worse than useless because they make it harder to spot and read the good comments.

I think the only thing worse than an uncommented codebase is a codebase full of comments that tell you what the code is trying to do in full detail, every few lines.....

[dahvyd]

I work at a shop where we use comments sparingly if at all. Our primary product has 14m LOC and 400k unit tests. We enjoy over 75% global market share in our extremely lucrative industry. We didn't get where we are today by being "lazy" as you put it. Comments are by very definition a redundancy when the code is perfectly descriptive and self-documenting. Thus developers can get on with their job and be more productive when they don't have to duplicate their efforts for dubious benefit.

[einhverfr]

The beauty of literate programming, quite honestly, is that because of the way that the documentation and code are interwoven, it requires fewer code comments, and encourages both clear code and clear documentation.