THE DATABASE APPROACH - Database Design and Development: An Essential Guide for IT Professionals - page 5

sector. All aspects of the technology have been improving tremendously. Here are
some specifics:

• Twenty-five years ago, there were only 50,000 computers in the whole world;
now more than 500,000 are installed every day.
• More than 60% of American households have at least one computer; more than
50% have e-mail and Internet access.
• Growth of the Internet and the use of the Web have overshadowed the PC
breakthrough of the 1970s; at the beginning of 2000, about 50 million house-
holds worldwide were estimated to be using the Internet; by the end of 2005,
this number is expected to grow 10-fold.
• About 7 years ago, there were only 50 websites; now 100,000 are added every
hour.
• Databases in the terabyte range are becoming common; a few years ago, even
the gigabyte range was unusual.
• In the mid-1960s, programmers in large corporations had to write programs that
had to run on 12K machines; today even your personal computer at home has
10,000 times larger memory.

Growth has not been isolated here and there in hardware and software. We notice
explosive growth in all sectors of information technology. Let us proceed further to
look at specific areas of information technology that are related to data systems.

Data Storage Devices Have you seen an 80-column card that very early com-
puter systems used to store data? Each column in a card had holes punched to
represent a single character. So a card could hold up to 80 characters. Keypunch
operators typed data and program code into the cards. In the next stage, computer
systems stored data on magnetic tapes. Initially, magnetic tapes of 800 BPI (bytes
per inch) were used. Then we moved on to higher densities of 1600 BPI and 6250
BPI. For a brief while, paper tapes with punched holes were used as the storage
medium. Special-purpose paper tape readers were used to read data from paper
tapes.
It was a large leap forward when disk drives began to replace the earlier data
storage media. Disk drives in mainframes consist of sets of large circular disks
arranged in parallel with a common spindle. Sophisticated disk drives have come to
stay as the common storage device of choice. Today's data servers use RAID (redun-
dant array of inexpensive disks) technology as the advanced fault-tolerant storage
system. Data storage devices have progressed tremendously from the primitive
punched cards to the sophisticated RAID systems.

Three-and-a-Half-Inch Disk Drives You are very familiar with the three-and-a-
half-inch disk drives in your home computer system. Just review the progress in the
capacities of these disk drives. See how the capacities kept doubling every year.
Note the following details:

1992 1 gigabyte

1993 2 gigabytes