1. Primary Storage: Memory
Primary storage is directly accessible by the processor
Memory:
RAM = random access memory
ROM = read only memory
PROM/EPROM = programmable ROM
RAM is volatile (not retained w/o power)
cache, interrupts, memory, flags…

2. Secondary: Mass Data Storage
primary storage is directly accessible by the CPU (RAM, cache memory)
secondary storage is not directly accessed
data is transferred to primary memory when needed by processor
MDS is non-volatile - record and modify information (semi-)permanently

3. Types of MDS Punched surfaces Magnetic surfaces Optical surfaces
- earliest method; human readable
- punched cards, punched tape
Magnetic surfaces
- most widely used
- streaming tape, magnetic disks (floppy, hard, zip…)
Optical surfaces
- most durable
- optical disks (CD-ROM, laserdisc, DVD…)

4. Comparisons of MDS types
media:
size/capacity:
advantages:
disadvantages:
Floppy
3.5” = 720KB, 1.44MB, 2.88
5 ¼” = 360, 720KB (old)
8” = 180, 360KB (old)
inexpensive;
shareable
slow;
effected by magnetic fields, dirt, temp; corruptible
Hard
¼, half & full height,
51/4”, 8”
= 5MB… 100+GB?
fastest
not usually portable;
not expandable
Optical
CD = 4.5” =
80-650MBdata/74minAudio
Laser = 8”,12”
DVD = GB
massive capacity,
high reliability,
portability,
data & audio standard
read only
Removable
Clik = MB
Zip = MB
Jaz = 500M - 2GB
SuperDisk (3M - Imation) =120MB
faster & more capacity than floppies;
read/writeable
slower than hard;
more expensive than floppies
Magneto-optical MO
combination of technologies
reliable;
high capacity
expensive;
not as fast
Flash Memory
(newest)
solid state storage;
memory sticks; flashcards
no moving parts,
rewritable
very expensive;
no standard yet