Chapter 2. PLACEHOLDING NUMERATION
The ENIAC did not use the binary system. Its arithmetic processor used vacuum tubes wired together into rings, which worked like old desktop adding machine wheels. These were base ten contraptions. Since then, however, all electronic computers have done their arithmetic using the binary system (base two). Consequently, descriptions of computer arithmetic are customarily expressed using the binary system or related systems such as hexadecimal (base sixteen) or octal (base eight). An understanding of these number systems is essential. Readers already familiar with them may prefer to skip this chapter.
The Decimal and Pentimal Systems
Before the invention of placeholding decimal notation in the East, probably in India ...