Terminal History

In the beginning

Once upon a time, before personal computers, before microcomputers, there existed mainframe and minicomputers. These were big expensive things and the use of each one was typically shared by many people.

In the earliest days (well almost) there would be several teleprinters connected to the computer. Each person who needed to use the computer could join a queue and get some time at a teleprinter. A teleprinter consisted of a keyboard and an impact printer that printed onto a continuous sheet of paper from a roll. Later ones may have used fanfold paper, I forget. Typically, stuff you typed in was printed in red, the computer’s answer was printed in black.

To edit a file, you’d give commands like “show me lines 12 through 15”, “delete line 13”, “insert the following text after line 12”, “on line 27 replace characters xyz with pqr”. Only you’d have to express it more cryptically (“p12,15” etc)

Terminals were connected to the computer using a serial cable. This used the RS232 serial standard (there were current loop interfaces but I never encountered any). These things typically ran at 300 characters per second.

Eventually, these paper based teleprinters were replaced by “glass teletypes” where the print mechanism was replaced by a screen, typically showing 24 lines with 80 characters each. This saved paper.

Intelligent Terminals

The glass teletypes were quickly superceded by “terminals” which were the same but with a lot more intelligence built in. You could move the cursor around and edit files visually. The computer could send commands to make the cursor jump to a desired location on the screen or to do a myriad of other clever things.

In the days I used them, these things could work at maybe 9600 characters per second.

Every computer manufacturer made terminals, they all had their own proprietary standards for moving the cursor around. They all had their own keyboard layouts. Specialist terminal makers arose to supply the market with better or cheaper alternatives.

Character cell Terminals

Nowadays, things have moved on and these terminals don’t seem to be so intelligent. hence the term character-cell terminals.

Terminals are still manufactured and are still in use. They are typically used for dedicated single function applications such as Point of Sale. They are much simpler than PCs and hence, more reliable. These days there’s not much of a price advantage though. Their era is drawing to a close.

Terminal Emulators

During their long decline, terminals were increasingly replaced by PCs running “terminal emulation” software. This actually worsened the problems described elsewhere on this page. Largely because terminals had grown so complex that few software developers emulated their features (and bugs!) accurately and completely. Also software developers liked to add new features , like colour).