You have to understand the context, and the time period. Memory and CPU cycles were precious. All computers being 24/7 networked wasn't a thing, so security wasn't much of a concern. API design tended to reflect that.
Not mentioned in my initial comment, but yeah, I'm viscerally aware of the affect the time period and resources at the time have on API design in C and other languages from that time period.
The null pointer in place of the operand here just seemed like a really good quirk to point out
The null pointer in place of the operand here just seemed like a really good quirk to point out