Identifying Physical Media

Revision as of 01:24, 31 October 2012

One of the first steps in the process of preserving information is recognizing it when you encounter it. Some media formats are more readily identified as such at first glance; others may not be identified as media at all and never investigated. Some categories and examples follow.

Mechanical Storage

Examples of mechanical storage would include records, punch cards, player piano rolls, and printed materials that may be machine readable. The range within this category combined with the wide variety of techniques used over the years makes it one of the more challenging categories.

Punched Holes

The punching of a hole in material to record information yields examples ranging from Hollerith cards to ticker tape machines.

Look for:

• generally more linear, either in separate card or continuous material form.
• the older the material the more likely the holes are to be visible

Waveform Encoding

Needles dragged in groves used to encode waveforms like the audio stored on a phonograph record.

Look for:

• Materials that hold a groove well ranging from wax to vinyl.
• Disk or cylinder shapes.

Printed Materials

Checks have magnetic ink used to store the routing information for the issuing bank. Computer hobbyist magazines used to print programs using Optar which is a 2D barcode.

Look for:

• high contrast patterns; similar to bar codes or QR codes.

Optical Storage

Optical can range from film to DVDs. Film stock may range from single frame slides to reels of film in either positive or negative print. Any celluloid material should be checked regardless of size and shape. More modern variants of optical storage may not be transparent such as CDs and DVDs.

Look for:

• celluloid
• it is possible that the holes may be filled with another material that is transparent to different wavelengths of light.

Magnetic Storage

Magnetic storage can take many forms including tape, floppy disks, hard drives. In general for this category there is physical motion of the relative position of the media and a read head. Look for either tape in reel form, enclosed reel, disk, or cylinder.

Look for:

• Brand names on packaging (BSF, Sony, DEC, Memorex)
• Reels of tape ranging from reel to reel to enclosed cassettes to TK50 tapes which are square tape enclosures designed for automatic mounting when placed into a reader
• floppy discs which can either be sheathed or enclosed in a plastic cover
• hard drives, but remember that these may take the form of disk packs designed to fit into machines the size of a washing machine.

Floppy Disk

Measure the disk:

• 8"
  • introduced in 1971
• 5 1/4"
  • introduced in 1976, ranged in capacity from 87.5KB to 1155KB (may be labeled as 1.2MB)
  • look for notches about 1 inch down from side opposite the read window, may be covered by sticker. These were used as read/write indicators. If they are on both sides the disk was designed to be flipped and reinserted. If on one side it may either be single or double sided.
• look for number (1 or 2) alignment windows near central drive hub hole.
• 3 1/2"
  • introduced in 1983, ranged in capacity from 280KB to 2.88MB
  • look for logos in the plastic cover using "DD" "HD"
  • read/write is via small movable piece of plastic in one corner
• 3"
  • introduced in 1982
• 2 1/2"
  • introduced in 1986
• 2"
  • introduced in 1989

Solid State Storage

Solid state storage can be small and its technology is largely shape independent. It can include USB flash drives, and solid state drives.

Look for:

• Connectors including USB connectors in their various forms.
• SIM cards
• SDcards