Storing computer data began with magnetic tape drives and evolved into magnetic disk and eventually solid state. However, tape is expected to thrive well into the future, primarily using Linear Tape Open cartridges (see LTO
). Following are the early storage technologies. See early memory
Magnetic Tape Was Endless
Files of any size were captured on reels of magnetic tape, and when one reel filled up, another reel was added. In the 1960s, a single data file could be contained on dozens of reels. Tape is a sequential medium, and all the records have to be sorted into some numeric or alphabetic order. To update a master file, say of customer records, both the master and transaction files are sorted into the same order and matched from A to Z in sequence (see batch processing
). Although it can be done, it is extremely time consuming to locate a record on tape reels. Robotic libraries full of tape cartridges have more direct access capability, but they came on the scene years later (see tape library
Datacenters Full of Tapes
In the 1960s, tape was the storage medium, and every computer had tape drives. (Image courtesy of The Computer History Musem, www.computerhistory.org)
Although magnetic disk storage did not take hold until the end of the 1960s, IBM actually introduced the first disk-based computer in the mid-1950s.
The RAMAC Disk Computer (1956)
Direct Access Tape Strip "Card" Storage (1960s)
At 2,000 bits per square inch, IBM's RAMAC was the first random access disk drive. Each 24" platter held 100,000 characters for a total of five million characters. See RAMAC
. (Images courtesy of IBM.)
Although RAMAC (above) was direct access, it was a stand-alone system that only held 5MB, and direct access to a single record in a large file was still a major goal. To that end, IBM, NCR and RCA introduced magnetic card storage that held more data than RAMAC and were peripherals to the computer systems already in use.
These mechanical marvels recorded strips of tape that were released from their cartridge, transported to a rotating drum for reading and writing and returned. Card jams were frequent, and within a few years, they were replaced with disk drives.
IBM's Data Cell
Each Data Cell held 10 cartridges on a rotating carousel for a total of 400MB, which was more storage than the NCR and RCA devices (see Data Cell
). (Image courtesy of IBM.)
Part of NCR's 315 computer system, CRAM cartridges held a modest 5.5 or 11MB of data (see CRAM
). (Images courtesy of NCR Corporation.)
The RACE system was a tape strip storage system that held a total of 250 million characters. RACE was the most error prone of the three card systems. If there was no jam all day, that was a very good day. Unfortunately, we found no images of these mechanical beasts, but if you have one, please contact Alan Freedman, author of this encyclopedia. Freedman was actually a salesman with RCA at the time but had no idea he would be chronicling the industry later in life. See RACE