[R] What is the 'scale' in princomp() function?

[Xingwang Ye]

Dear R users,
When I tried to use princomp() from stats packages to do Principal 
Components Analysis, I am not very clear what is the "scale".
And the scores are different from "PROC PRINCOMP" procedure from SAS.
 
Using the example data from this package:

restpc <- princomp(USArrests, cor = TRUE)
 > restpc$scale
Murder Assault UrbanPop Rape
 4.311735 82.500075 14.329285 9.272248
 > sd(USArrests)
 Murder Assault UrbanPop Rape
 4.355510 83.337661 14.474763 9.366385

Why 'restpc$scale' is different from 'sd(USArrests)'?

felix