# read the R script
    > source("cachematrix.R")
    
    # create a square matrix
    > a <- makeCacheMatrix(matrix(c(11,22,33,44),nrow = 2, ncol = 2));
    
    # or
    > a <- makeCacheMatrix()
    > a$set(matrix(c(11,22,33,44),nrow = 2, ncol = 2))
    
    # get the matrix
    > a$get()
         [,1] [,2]
    [1,]   11   33
    [2,]   22   44
    
    # compute the inverse. 1st time: real computing
    > cacheSolve(a)
                [,1]        [,2]
    [1,] -0.18181818  0.13636364
    [2,]  0.09090909 -0.04545455
    
    # compute the inverse. 2nd time: getting the cached value
    > cacheSolve(a)
    Getting cached data...
                [,1]        [,2]
    [1,] -0.18181818  0.13636364
    [2,]  0.09090909 -0.04545455