I produced this lecture was several years ago. While many of the concepts are okay, much of the specific detail is ancient history (i.e. hard drive size). Can you tell what's totally out of date?
Primary Storage
The memory that holds instructions and data for immediate use by the CPU. Primary storage (memory) elements include RAM, cache, and other volatile memory locations (such as registers) whose content is lost when the computer's power is shut off.
Secondary Storage
The magnetic or optical media that store programs and data permanently through the operations of secondary storage devices generally referred to as drives. Secondary storage is nonvolatile, meaning that instructions and data are retained regardless of whether the computer is turned on or off.
Comparison of Primary and Secondary Storage
***PRIMARY STORAGE***
***SECONDARY STORAGE***
Internal (on system board) External (usually mounted in tower) Very fast (nanoseconds) Relatively slow (milliseconds) Volatile Non-volatile Limited (expansion slots) Unlimited Expensive ($$ per MB) Inexpensive (¢¢ per MB)
Secondary Storage Devices
|
***COMMON SECONDARY STORAGE DEVICES*** |
||
| Hard Drive (c:\) | 20GB & up | Magnetic - data stored on platters in a sealed unit |
| Floppy Drive (a:\) | 1.44MB | Magnetic - data stored on mylar in hard plastic casing |
| Tape Drive | Various | Magnetic - data cassettes |
| ZIP Drive | 100/250/750MB | Magnetic |
| JAZ Drive | 1GB | Magnetic |
| CD-ROM Drive | 700MB | Optical - read only (80 min. music) |
| CD-RW Drive | 700MB | Optical - read/write |
| DVD Drive | 4.7GB | Optical - read only (movie) |
| DVD-RW Drive | 4.7GB | Optical - read/write |
| Compact Flash Drive | Various up to 200MB range | Magnetic - digital cameras |
| Jump Drive | Various up to 200MB range | Magnetic - plugs into USB port |
Storage
|
***STORAGE SPACE*** |
| Bit - smallest unit of data equivalent to a single zero (0) or one (1) |
| Byte - a group of eight (8) bits |
| Kilobyte (KB) - approximately one thousand bytes (1,024 to be exact) |
| Megabyte (MB) - approximately one million bytes |
| Gigabyte (GB) - approximately one billion bytes |
| Terabyte - approximately one trillion bytes |
Processing Time
|
***SPEED*** |
| Second (sec) - 60 per minute |
| Millisecond (ms) - one thousandth of a second (Floppy Drive) |
| Microsecond (µs) - one millionth of a second (Cache) |
| Nanosecond (ns) - one billionth of a second (the CPU) |
| Picosecond - one trillionth of a second (getting close!) |
|
***MICROPROCESSOR SPEED*** |
| Gigahertz (GHz) - one billion cycles per second (Hertz is a unit of frequency) |