Turbo Pascal was made famous specifically because it skipped the assembly step (as well as most of the linking step). In a single pass it created raw, absolute located binary code and saved a lot of time. This is one aspect that made Turbo particularly fast. Action! on the Atari was very similar.
The time was saved mostly by skipping the I/O, especially to the then glacially slow and low capacity floppy drives of the day.
Compiling to assembly removed a litany of issues from the compiler. The compiler could pretty much blindly emit opcodes and pseudo-opcodes. The assembler and linker were joined at the hip, having to work with the shared experience of managing an object file, which contained both binary code, symbols, and relocation information.
Since the assembler and linker are so closely entwined, the assembler acts as a level of abstraction between the compiler and linker. This also allows the assembler and linker to diverge and improve apart from the compiler. As object file formats evolved, the compilers had to at best make only minimal changes (to perhaps update the meta data as manifest by assembler pseudo ops). Whereas were the compilers writing object files directly, then now all of them have to be updated as the linkers et al improve.
Turbo Pascal was able to target the very simple system that is CP/M, with its absolute memory layout and not need many of problems that a linkage step solved. Turbos solution to code reuse was simply the include file (and they sold several Toolboxes of utility source code to incorporate directly in to you applications rather than precompiled binary code that could be linked).
It wasn't until Turbo Pascal 4 that Turbo actually started to involve a formal conventional link step in to the process (via the addition of Units).
Addenda for comment:
most practical programs would be small enough to be handled by a
Simply put "small enough" is solely dependent on the speed of the machine doing the build. Linking pre-compiled objects is faster than compiling source code. At some point, the time it takes to incrementally rebuild and link a final executable will be faster than recompiling everything, all the time. As machines got faster, the size of that program grew. But machines were not always fast.
Back in the day, Moria (a dungeon crawl "roguelike" game) was distributed on DECUS tapes in source and binary. The source was 22,000 lines of VAX Pascal. Our tiny VAX 11/730, on which we did a remarkable amount of daily work (with up to 10 users), simply could not compile that program before the universe achieved heat death (at least it felt that way). Were it built as a bunch of modules that were linked together, we might have had a chance to dabble with it. But on our machine, it wasn't practical.
However, on the authors machine, a VAX 8600 (far far bigger), it was, demonstrably, not an issue. Since it wasn't an issue, he never bothered to break the program up. If he had, then maybe (maybe) we'd have had a remote chance of being able to build and iterate and play with the source code.
You also have to consider other aspects. When doing development on a large program on a PDP-11/70, my friend and I would have 3 terminal sessions open. One to run the program, one to edit the program, and one to compile the program.
We did that simply because getting in and out of the editor was glacial due to the size of our file. When it started up, the editor (on our 1200 baud terminal...) even noted "Loading xxx.yyy slowly...", and it wasn't kidding. Even then we still had to manually page blocks in and out of active memory. It would have been awful if we had to weather reloading that editor every compile cycle. Compile time alone was bad enough if a simple typo slipped in.
I can't say whether we could have done multiple source files with incremental build and link for our program or not -- we were just college students bumbling our way through it. I don't even know if it was possible with that particular dev environment (probably, but we may not have got that far in to the back of the manual). But it just stands as an example that highlights how small the definition of "small enough" can truly be, and how fast one can outgrow the tools.
Oh, just how big WAS our program? 35K of source code.
All of these tools were built to facilitate productivity, and the domain of those tools was REALLY BAD hardware. It's amazing anything was accomplished at all in hindsight, but that's just looking backward with jaded eyes.
I ran the compile/assemble/link cycle on a C environment for the Atari 800 — once. It was completely unusable it took so long.
I have a current Turbo Pascal project, it's around 1200 lines of code. It's in several include files. On a simulator, running a simulated 4Mhz CPU, this takes 1-2 minutes to build. But, while the CPU is simulated at 4MHz, the I/O is my "XXX Gbps" hardware, vs 2000 Bps (if we're lucky) floppy drive. It would be even slower on a "real machine", since it has to read all of the files and write the final .COM file each build, vs normal Turbo compiling a memory based program in to a memory based executable. 1–2 minutes isn't bad. Human scale, it's ok. But 10 lines per second? Nothing to brag about. But in the end I have no choice because of how TP is structured and its feature set. This will not get any faster outside of porting to something else, and who knows at what point that would be.
It's not 20 minutes, thank heavens for that.