A distinguishing feature of computer systems is memory capacity measured in bytes. Initially, memory was measured in thousands of bytes, or kilobytes. Then it rose to millions of bytes, or megabytes. Hard disk memory capacity then reached thousands of megabytes, known also as gigabytes. Already the market has introduced a newer level of memory called terabyte. This represents about a thousand gigabytes of storage space.
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Memory and Storage
The capacity of both memory and storage drives are measured in bytes. The memory on a computer, known as random access memory, or RAM, is much smaller than a hard drive because it only stores information temporarily. Thus, while a typical Windows 8 computer in 2014 is measured in terabytes, or TB, the RAM is only measured in gigabytes. The average computer would have, for example, 2 GB of RAM and 1 or 2 TB of hard drive space.
Computers of the early 1970s had memory capacity in the Kilobyte range. A kilobyte (K) is one thousand bytes approximately. Thus, K represents 1,024 bytes of storage or memory capacity. In practical terms, a word processing document with 250 words and no graphics is approximately 7K. Microsoft Word will count the words and give you the memory capacity of the document.
In the 1990s, hard disk memory reached the megabyte range. A megabyte (MB) is approximately 1,024 K. This comes to about 143 pages of a word document without graphics. Thus, a 100 MB memory stores about 14,300 pages of Microsoft Word documents.
Until a few years ago, most hard drives were measured in GB. USB flash drives are still measured in GB, as is memory. A single GB is 1,024 MB, which is the same as 1,073,741,824 bytes. This equals, in practical terms, to about 143,000 pages of a Microsoft Word document without graphics. Thus, a hard disk of 100 GB is equivalent to 14,300,000 pages of stored document.
In 2007, hard disks with terabyte capacity were released into the market. A TB is 1,024 GB. In practical terms this comes to about 143 million pages of stored Microsoft Word documents. One TB is the same as over one trillion bytes, or 1,099,511,627,776 bytes. With such large storage capacity, we enter a new world of computing power. Terabyte storage makes digital libraries a reality in a very small space. A terabyte hard disk occupies a less than 4-inch by 1-inch footprint.
Bigger than Terabytes
The computer industry is already preparing for more storage in the future. A Petabyte is 1,024 TB. An exabyte is 1,048,576 TB. An exabyte is so large that if someone wrote down every word ever spoken by every human being who ever lived, that would be about 5 EB of data. A zettabyte is 1,073,741,824 terabytes. If all of those words spoken by everyone who ever lived was recorded in MP3 audio format, this would be about 42 ZB. A yottabyte is 1,099,511,627,776 TB.