This is my summary of the inventions I learned about in lessons one hundred seventy-one through one hundred seventy-four.

In lesson one hundred seventy-one, I studied the invention of flash memory. Originally, computer memory took up a lot of space and was unwieldy. It looked like a large barrel, and it was expensive. After that, core memory was invented, and it was basically a string of magnetic beads. After that was solid-state memory, but it was still rather inefficient.

This was changed in 1981 when Fujio Masuoka invented flash memory for Toshiba. He wanted to improve EEPROM, which was a form of computer memory that retained information even when without power. It was slow, though, so Masuoka invented flash memory as an alternative. Flash memory is much faster than older forms of memory, and it can be written and erased quickly without having to delete everything.

In lesson one hundred seventy-two, I learned about the CD-ROM. After inventing the audio CD, the CD-ROM (Compact Disc Read-Only Memory) was invented by companies Phillips and Sony together in 1985. A CD-ROM is a computer disc used to store digital information.

In lesson one hundred seventy-three, I studied the invention of the handheld cellular phone, also called the cell phone. Before the cell phone was invented, there was the telephone. It could be used to communicate over large distances, but you could only move a few feet away with it. This wasn’t exactly convenient, as you couldn’t just carry your phone along with you to make an emergency call if necessary. Eventually, car phones were invented, but they were extremely inefficient.

Martin Cooper invented the first handheld cell phone in 1993. It weighed two and a half pounds and could only supply twenty minutes of talk time before it required a ten-hour recharge, but people loved it. Today, people couldn’t live without it.

Last of all, lesson one hundred seventy-four was about the invention of the World Wide Web. It was invented in 1989 by Tim Berners-Lee. He first invented the idea of it by saying someone should combine the Internet and hypertext, but no one did – it was considered too difficult. Berners-Lee finally took it up himself, the result being the WWW (World Wide Web). If he had simply given up, life would (sadly) be much more difficult. We wouldn’t be able to click across the Internet so quickly without it.