Originally posted by jettredmont
In case you're not joking:
You have a good description of vectors in physics; unfortunately "vectors" in computers are a completely different beast.
In computing terms, a "vector" is an arbitrarily-sized array of values. A "vector unit" will typically deal with vectors of 32-bit ints, 16-bit ints, 8-bit bytes, and 32-bit floating point numbers more efficiently than by dealing with each element of data individually. In Altivec, the vector processing size is 128 bits, so if you have 32-bit ints in your vector the Altivec unit can process those ints four at a time (4x32 = 128). However, you can only do this when you are doing the same thing to every int (for instance, multiplying each by 3). Another name for a vector unit is "SIMD", which stands for "Single Instruction, Multiple Data".
This is a good thing for "multimedia" applications as they often do the same thing on multiple bits of data. Other apps ... well, there's not much opportunity for SIMD in a word processor, for instance.
No, I have no idea why they chose the name "vector" for this, but they did, and we must live with it 🙂 The term persists in several computer languages as well (C++ and Java, for instance).