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Your being downvoted but you have a valid point. People should look up the NTSC/PAL standard for how analog TV screens worked. There were only ~560 scan lines
by IIAOPSW 7y ago
Your being downvoted but you have a valid point.
People should look up the NTSC/PAL standard for how analog TV screens worked. There were only ~560 scan lines in the raster pattern (vertical and horizontal blanking intervals notwithstanding). With a character height of 7 pixels/scan lines + one for spacing that gets you 70 lines of text on screen. Even if the punch card machines gave you more memory, actually using it would have required buying a special purpose TV. Eventually we did get CRT monitors which were specific for computers instead of television, but that wouldn't be economically viable at the time.
- tyingq 7y agoThe downvoting is likely because 80x24/25 happened well before home PCs that displayed via NTSC/PAL. And many of those early terminals also supported a 132 column mode.
- IIAOPSW 7y agoWhat were the earlier non-home computers displaying on?
- tyingq 7y agoCRT, but not via RF modulators, NTSC, PAL, etc.
- IIAOPSW 7y agoThat's very odd. Why did they invent a new CRT format and spend the cost of the hardware to implement it instead of using an off the shelf TV?
- tyingq 7y agoBecause TVs didn't have high quality video inputs. Old Apples, C64s, etc, came with a "tiny tv broadcaster" (RF modulator) that broadcast the signal on channel 3. In shit NTSC or PAL quality, which is lower resolution than what the CRT can display.
- IIAOPSW 7y agoI understood that. I'm old enough to remember VCR's / game consoles required you to turn to channel 3 or 4. But what were the older, non-personal terminals using? Was there some sort of RF modulated raster pattern optimized for displaying text? Were they drawing everything as vectors? Did they use off the shelf CRT's?
- tyingq 7y agoDirect manipulation of the beam with analog voltage to a CRT driver for the x and y axis. Same as what the TV does inside.
- PixyMisa 7y agoThey just took a regular B/W CRT and wired it up directly - leaving out all the PAL/NTSC decode circuitry. That allowed for a much sharper picture.
- yodon 7y agoAnalog TV's required incredibly high bandwidth electronics, which was standardized to meet TV requirements. The early terminals used TV hardware in custom cases they just plugged in directly rather than going through the demodulators used by home PCs once they were invented.