A Brief Overview of Computer Storage

The first computer was designed by Charles Babbage in the early 19th century. It was mechanical, not electrical, and was too complex at the time to be built. The computer was called a difference engine. A working version of Babbage’s first design has now been built and resides in the Science Museum in London, England.

Another 19th century inventions which was later used by the first computers was the Punchcard. This is a card which is used to store data. Interestingly, this invention was used to store and analyse data from a national census in America in the late 19th century. The card is laid in a landscape orientation and broken into vertical columns, each column contains a pattern of holes used to represent a character, and each character is represented by a unique pattern of holes. The card is read by passing it over a series of lights where there is a hole the light shines through onto a light sensitive cell beneath, where there is no hole nor light reaches the cell. These cells therefore, generate a series of electrical charges which the computer can read.

It can be said that the Punchcard is a 2-state device, as the patterns which the computer can detect are made up of 2 different options, a hole in a certain position on the card or no hole; therefore each light sensitive cell either generates an electrical current or doesn’t! Many other 2-state devices are possible, in fact 2-state devices are so numerous and reliable, all modern computers use them.

Computers may store data in many forms;
• Numbers
• Letters
• Pixels
• Sounds

They are all stored in this way. To help us understand what the computer is storing, we can use a different form of counting called binary.

Binary numbers are somewhat strange as the only 2 numbers you can use are 0’s and 1’s. It is, however, possible to represent all of the above data using binary. For example: the number 13 can be represented by the binary code 1101. Normally, we consider groups of binary numbers in strings of 8, the number 13 would therefore be 00001101. A set of eight binary numbers is called a byte, each individual 0 or 1 is called a bit. The term byte maybe familiar to you, we more often talk of kilobytes, megabytes and gigabytes.