Across

3. GROUND—GND
5. MR—Modem light; "Ready"
7. CARTER—Former U.S. president (b. 1924) with a background in nuclear physics and the study of reactor technology. Hint: "39"
10. BAFFLE—A partition, or screen, placed between a microphone and a source of sound.
13. CHARACTER—A punctuation mark, number, letter, or symbol.
14. OCTAGON—Eight-sided polygon.
15. ILLEGAL—A character that you are not allowed to use when naming a file.
18. TITANIUM—A low-density white metallic element.
21. HIERARCHICAL—The H in H-menu.

Down

1. FORUM—A place online where you can meet other engineers and discuss important topics and ideas.
2. EXABIT—1,000,000,000,000,000,000 bits
4. SNAILMAIL—Postal delivery. Hint: mollusk
6. RAMAC—The IBM computer introduced in 1956 that featured disk storage.
8. EIGHT—Twenty-four is the least common multiple of 12 and which number?
9. BAT—Extension for a batch file.
11. ERGONOMICS—Field of study that deals with how humans interact and work with machines.
12. KATIE—The dog Circuit Cellar founder/editorial director Steve Ciarcia has mentioned in his editorials.
16. BTW—Text message: "By the way."
17. MACTEL—A PC that features an Intel processor and a Mac operating system.
19. IMHO—Common text message: "In my humble opinion."
20. SCSI—A standard for connecting peripherals and PCs. Hint: "scuzzy"