Old Computers


AudioBoom link: https://audioboom.com/boos/4291468-in-the-good-old-days-computers

When I was in college from 1971 to 1975, NONE of these existed: personal computers, floppy disks, hard drives, CDs. So how in the world did we save our computer data? Well, we had two methods: punched paper tape and punched cards. That sounds crazy, Teacher Lee. What are you talking about?

Mainframe Computer

Without personal computers in college, all students had to share a single huge computer called a mainframe computer that was kept locked up in a computer center on campus. It filled an entire room (but was probably less powerful than our home computers today).

Teletypes, and Punched Paper Tape

To talk to this mainframe computer, we would type in computer commands (called a computer program) using a remote input/output (I/O) machine called a teletype. A teletype was a big, clunky console with a keyboard that required considerable force to push the keys down. The teletype had its own built-in printer for visual printed output. The teletype was not a computer itself. It was simply an I/O terminal that allowed you to use the services of the huge mainframe computer.

  • Input: Keyboard.
  • Output: Data could read from or written to a punched paper tape. In addition, there was a roll of paper that served as a built-in printer. Output could be printed here for viewing only.To save data, the teletype would punch holes in a paper tape in Write/Output mode.
    To read data, it would read the holes in the paper tape in Read/Input mode.In the teletype below, you can see a paper tape slot at the lower left corner of the teletype. The paper tape reader can read 1-inch-wide, yellow paper tape with holes punched in it.

Below is a short video that shows a teletype saving a program to paper tape while also printing output to the teletype printer.

Punched Cards and Card Readers

What if you dont have access to a teletype?

Well, then you have to get really primitive and use punched cards. Instead of using a teletype to read a paper tape, we would use a special card punch machine to punch holes in stiff cards about the size of an envelope, based on our keyboard input. This generated a stack of punched cards. The mainframe computer had a punched card reader that could then read our computer program into its data banks (giant hard drive).

This is a punched card with data holes punched into it. Each column of holes and non-holes is one character. This card holds about 60 typed characters.

A card punch machine looks like this:

Watch the first 1:25 minutes of this video to see a card punch machine in action.

For the mainframe computer to read our punched cards, it had a punched card reader. The following video demonstrates a punched card reader. It is a commercial product demonstration video and is about 2 minutes long. Please be patient.

Below, you can see that this programmer has a large stack of punched cards to feed into the computer as input.

My First Personal Desktop Computer

My first personal desktop computer was the TRS-80 Model I, sold by an American electronics store chain called Radio Shack. Some people called this the Trash-80, whether as an insult or a speaking convenience, Im not sure. I bought one around 1981. It used the BASIC computer language as its operating system (OS). It had a black and white monitor (only 2 colors is called monochrome; “mono” = one; black is not considered a color for this purpose). So, how do I load and save my computer programs on this new smaller invention? Study the equipment below. Do you recognize that device on the left with the red button? From my previous blogs, you should recognize that as an audio cassette player/recorder.

Yes, an audio cassette tape player/recorder was needed for I/O on this computer! The computer could convert data to sound for saving and sound to data for loading/reading. It had a sound jack just like your cell phones do today. To save, I would record the sound from the Sound Out (earphone) jack onto an audio cassette tape. To load, I would play the sound from the audio cassette tape into the Sound In (microphone) jack. Zany, huh?

My First Portable PC (not a laptop, just a portable)

My first personal, portable computer is shown below. It closed up into a “suitcase” shape for carrying. It weighed about 40 pounds (18 kg)! This was long before Windows existed, so its operating system (OS) was DOS (disk operating system). Note it came with a 10MB hard drive, which is minuscule by today’s standards, but was huge back then. Its RAM (random access memory) was only 256 KB (about 0.25 MB). The monitor was monochrome; it had two colors, green and black.

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