IBM R30 Operator's Manual page 30

Types of 3.5-Inch Diskettes
Attention: Diskette drives and diskettes must be the correct type to store data successfully.
If you use the wrong diskette in your 3.5-inch diskette drive, the data on the diskette could
be destroyed. Some computers operate with 720K-byte diskette drives (no printing on the
diskette-unload button) and use only 1M-byte capacity diskettes. If you are going to be
transferring work between computers that have different diskette drives, be certain the
diskettes are compatible. For more information, refer to your operating system manual.
The diskette drive uses the following 3.5-inch diskettes:
1.0MB capacity (stores approximately 720KB of data)
2.0MB capacity (stores approximately 1.44MB of data).
Refer to Appendix A for the diskette part numbers.
A 1MB diskette looks like this:
May Be Labeled 2HC
Write-Protect Slot
A 2MB diskette looks like this:
Sliding Metal Shutter
Write-Protect Slot
2-10
Operator Guide
Sliding Metal Shutter
May Be Labeled HD
Rectangular Cutout