hptsb
One of the earliest and most influential deviations from the original Dartmouth BASIC, the Hewlett-Packard Time-Shared BASIC was a cheaper, minicomputer-based and very popular alternative time-sharing system for the late 1960s.
Probably the first big split caused in early BASIC implementations was HPTSB's way to manipulate string variables. All string variables had to be explicitely declared with DIM, and from then on they should be dealt with as "arrays of characters", much like the C language would work when created some few years later. As a side effect, arrays of strings were not supported.
"HP-style strings" were adopted by some early microcomputer BASICs such as Apple BASIC, Atari BASIC and Sinclair ZX-80, in contrast with implementations which took inspiration from DEC's BASIC-PLUS string handling, especially those derived from Micro-Soft BASIC for the MITS Altair.