I've written little BASIC programs without an interactive debugger--I mean, it was an Apple II after all--but I can't imagine having to write any serious software today without a debugger. I have tremendous respect for those who did. It feels like I'm cheating somehow. :-)
Try machine language without an assembler. Welcome to hell.
After having supported Control Data operating systems for 15 years with other companies, I was hired by CDC in the early 80’s. One of their software experts came into my cube the first day with a Peripheral Processor dump and asked me to look at it. After a couple of minutes, I looked up at him and said, “This has to be off a NOS/BE operating system.” He asked ,”Why?”, and I said, “Because no NOS proggrammer would even think to do code modification on the fly, but it’s done by NOS/BE programmers all the time.”
He said, “You passed the test.” We became best friends.