Fortran dominated the world of computing in the 1960s, and early 1970s, but even though it is still widely used in scientific circles, it not continue to dominate the programming world. One the core reasons might be the rise of the personal computer in the late 1970s and beyond. People were now able to write programs at home on their (probably quite expensive) personal computers.
Fortran wasn’t popular because it was a compiled language – which meant that in the world of the early 80s, a Fortran program could take 10 minutes to compile on a system which used floppy disks. Once compiled, the Fortran program would offer fast execution. Interpreted languages on the other hand, were slow to interpret the program, but this likely was less of an issue as interpreted programs were often small enough that the speed they ran at was not an issue. Fortran’s libraries such as the math library also consumed large amounts of memory. The micro world was to be dominated by the easy-to-learn BASIC, and later by the likes of Pascal. This was augmented by the fact that many home systems of the 1980s had a ROM-resident BASIC interpreter, making it easy to write BASIC programs. Fortran did make an appearance in the form of a few compilers for the PC, such as MS Fortran, but just didn’t make the inroads of BASIC, or Pascal, in the form of Turbo Pascal family of languages.
The other issue was Fortran’s unstructured nature. As the industry moved towards structured programming in the early 1970s. the two core languages designed in this context, Pascal and C were making inroads. By the time Fortran became more structured with Fortran 77, the damage had been done. Fortran would evolve and carve out a niche in scientific programming, but would not dominate programming as it had in the 1960s.