Zenith Z-170, Owner'S Manual, Page: 18 / 147

12
Operation
Memory: The Three Types
Your computer comes with three types of memory chips. They differ in
what they're for, how they store information, and how much of each is
included.
ROM
- Read-Only Memory implies that the computer can read the con­
tents of these chips, but can't write anything new into them. ROM chips
are permanently "burned" to hold information that the computer needs
all the time. Specifically, they store the instructions for booting the com­
puter, showing the World Map Display, running the calculator, appoint­
ment calendar, and the phone directory.
Dynamic RAM
- This type of Random Access Memory holds information
that changes very rapidly. When you run WordS tar, the WordS tar programs
are copied from the program disk into RAM. A document you type is
also stored in RAM. When power is lost, or when you reset your computer,
everything in RAM is lost. That is why data and programs are always
stored on disks.
Non-Volatile RAM - NVRAM is a special type of RAM that is kept intact
with a small battery built into your computer. The contents of NVRAM
are
not
lost with a power interruption or when you reset your computer.
The NVRAM mainly stores the phone directory and your appointment
calendar.