PLS_INTEGER v/s Other Numbers ?

Question

Hi Gurus.
Following is a excert from Doc.
"When you need to declare an integer variable, use the datatype PLS_INTEGER, which is the most efficient numeric type. That is because PLS_INTEGER values require less storage than INTEGER or NUMBER values, which are represented internally as 22-byte Oracle numbers. Also, PLS_INTEGER operations use machine arithmetic, so they are faster than BINARY_INTEGER, INTEGER, or NUMBER operations, which use library arithmetic "
It says use pls_inter because
1) Others are 22-byte,qtn is what is the storge for this
2) Pls_integer uses machine arithmetic and others library arithmetic
qtn is what is the basic difference?
pls elaborate it for more clear idea.
Thanks for Reading the Post.
Raj Ganga

Answer 1

1. Storage for the PLS_INTEGER would be 4 bytes, I guess, since its range is [-2^31 .. 2^31].
2. Machine arithmetic is performed by the actual hardware ie. by the CPU (or some co-processor). Arithmetic requiring libraries is done at the OS level, I guess. Anyway, the point is "machine arithmetic" is at (pretty much) the lowest level in the computer's architecture, so it is without a doubt the fastest.