ASCII won by giving every machine one agreed 128-character code.

In the early 1960s each computer maker used its own character code, so a file or terminal from one vendor often could not talk to another. Robert Bemer, an IBM programmer, was a member of the American Standards Association committee that set out to fix this.

The committee chose a 7-bit code: 128 unique strings of ones and zeros, each mapping to a letter, digit, punctuation mark or a control function such as a carriage return. Using seven bits instead of eight kept transmission costs down, so it was cheap enough to become the default.

Once published in 1963, ASCII allowed machines from different manufacturers to exchange data, and it spread across terminals, printers and operating systems. It became the common encoding that early computing built on, even though it only covered the English alphabet.

One universal code beats many private ones

A single agreed code meant a character meant the same thing on every machine.

Seven bits made it cheap to transmit and implement on the low-cost hardware of the day.

Being an open ANSI standard let any maker adopt it without paying anyone.

IBM and the wider industry backing gave it a large installed base quickly.

When interoperability is blocked by incompatible encodings, an open standard that everyone can implement for free beats a richer but proprietary alternative.

ASCII became the baseline encoding of computing and the basis for later extensions. Its limits - 128 characters, no non-Latin scripts - eventually drove the development of Unicode, which itself kept ASCII as its first 128 characters.