a cartridge drive is the IBM 2310, used on the IBM 1130. Disk cartridges were made obsolete by floppy disks. Alignment Disk drives with exchangeable disk packs or disk cartridges generally required the data heads to be aligned to allow packs formatted on one drive to be read and written on another compatible drive. Alignment required a special alignment pack, an oscilloscope, an alignment tool that moved the read/write heads, and patience. The pattern generated on the scope looks like a row of alternating C and E characters on their backs. Head alignment needed to be performed after head replacement, and in any case on a periodic basis as part of the routine maintenance required by the drives. The alignment pack was usually called the "CE pack," because IBM never called their 'service technicians' 'repairmen,' but "Customer Engineers" (CEs). And, since the alignment pack was only to be used by CEs, it was called the "CE Pack." Special CE media was also available for tape drives and diskette drives, known as "the CE tape" and "the CE floppy." Later drives with exchangeable packs (such as the CDC 8" Lark drives) embedded the servo with the data and didn't require regular head alignment. See also History of hard disk drives References IBM 1311 disk storage drive, IBM Archives Thomas G. Leary, "Transporting and Protecting Cases for Drum and Disk Records," , 1965; R.E. Pattison, "Portable Memory for Data Processing Machine," , 1965 Rotating disc computer storage media History of computing hardware Computer-related introductions in 1961