It is suggested that one should use only four fingers (index finger to little finger) to type letters and numbers, while the thumbs are only used for spaces and other keys in the bottom row. Also, it is thought that one would type better if they always use the same finger for the same key.
However, with the
Shift being located where it is, one could only press it with their little finger, which means that e.g. to write
Z? on QWERTY keyboard one should either do an extra inconvenient keypress (right-shift plus
z, then left-shift plus
/) or to use their little finger to hold some of
Shifts for the whole time, and then use the corresponding ring-finger to press a key that is normally typed by little finger.
It seems to me much more natural when both
Shift keys are located on the bottom row (e.g. in place of the
Alt keys), so that they could be pressed by thumbs. Since
Alt keys are used in shortcuts mostly, switching
Alts seemed to improve typing speed and accuracy for me (once I got used to it).
The question is: why on the IBM PC Keyboard (which has the bottom row),
Shift key is located where it is, just below the home row? Is there any rationale for it besides the fact it was located there on the typewriters?