Computer Data Storage Through the Ages -- From Punch Cards to Blu-Ray
SD Memory
Secure Digital cards were conceived as a competing format against Sony's Memory Stick and appeared on the storage scene in early 2000. Based on Toshiba's MultiMedia Card format (MMC), flash memory SD cards added DRM encryption features, are almost twice as thick as the slimmest MMCs, and offer faster transfer rates. Early SD cards were limited to just 32MB and 64MB capacities, but have since scaled to 32GB in high capacity SDHC cards. Moreover, a new specification called SDXC (eXtended Capacity) promises a new capacity ceiling of 2TB.

Approximate Years in Use: 1999 - Present
Maximum Capacity: About 32GB
USB Flash Drive
Arguably the most significant storage innovation since the 1.44MB floppy disk, the advent of USB flash drives in 2000 signaled the eventual end of the road for floppies. It wasn't the 8MB capacity at debut that won over power users, but the ability to boot from a USB key and, even more importantly, update a motherboard's BIOS. Vista holdouts still running XP with a RAID array are one of the few who still rely on a floppy drive, but it's far more common today to spot a modern build without a FDD installed, and it's all because of the USB flash drive. Way to go, killer.

(Image Credit: Corsair)
Approximate Years in Use: 2000 - Present
Maximum Capacity: About 64GB
HD-DVD
For a short while, the now defunct HD-DVD standard looked to be the front runner in the high-definition format war. Sure, the first HD-DVD players released in 2006 were incredibly high priced, but once early adopters ran up their credit card bill, player pricing promptly went into a free-fall. At one point, Wal-mart even sold a sub-$100 unit. On the technical side, HD-DVD made use of the 405nm blue-violet laser operating at the other extreme of the visible light spectrum than the 650nm red laser employed by standard DVDs. This allowed HD-DVD media to squeeze up to 15GB of data on a single-layer disc and 30GB on dual-layer discs, compared to the standard DVD format's 4.7GB and 8.5GB limits. But one by one, studios withdrew support in favor of the competing Blu-ray format, forcing Toshiba to wave the white flag and leaving a million HD-DVD owners feeling pretty pissed off. You might be one of them.

(Image Credit: Toshiba)
Approximate Years in Use: 2006 - 2008
Maximum Capacity: About 30GB(dual-layer)
Blu-ray
To the victor go the spoils, and in the high-definition format war, the victor is Sony's Blu-ray format. While Blu-ray was first introduced in 2002, the BD-ROM specifications wouldn't become finalized until 2006. Like HD-DVD, Blu-ray also makes use of the shorter wavelength blue-violet laser compared to standard DVDs. But unlike HD-DVD, Sony decided to modify the disc structure to allow for a higher value numerical aperture of the objective lens from 0.60 to 0.85. Both standard DVDs and HD-DVD consist of a 0.6mm disc with a 0.6mm protective layer, but Blu-ray media measures 1.1mm thick with a 0.1mm protective layer. The end result is that Blu-ray can store up to 25GB on a single-layer disc, at the expense of compatibility on the media assembly line. Despite the higher cost of both the media and players, Sony was able to convince studios to back Blu-ray exclusively and push HD-DVD into the same fate as Betamax.

Approximate Years in Use: 2006 - Present
Maximum Capacity: About 50GB (dual-layer)