Yes, exactly.

We used a set of INT instructions in well-known low memory addresses that all jumped to the same place. We had an ASM file that you linked with, that had sixteen different address combinations for each.

The common entry point would look back on the stack and calculate from the return address which entry point had been called, and run the appropriate kernel call. We called it the CS:IP hack.

In the context of this post, the DOS INT10 and INTx(I forget) required the caller to load registers with the desired system call number, then perform the trap instruction in their code. Fortunately CTOS didn't need those particular software interrupts, so I could implement them for my purposes.