diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..ab78bd20baf 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,36 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
+## Pair of functions to cache a matrix inverse calculation
+# example of use:
+# m = matrix(rnorm(100),nrow=10)
+# m = makeCacheMatrix(m)
+# mi = cacheSolve(m)
 
+## Creates a special "matrix" object that can cache its inverse
 makeCacheMatrix <- function(x = matrix()) {
-
+  m <- NULL
+  set <- function(y) {
+    x <<- y
+    m <<- NULL
+  }
+  get <- function() x
+  setinverse <- function(inverse) m <<- inverse
+  getinverse <- function() m
+  list(set = set, get = get,
+       setinverse = setinverse,
+       getinverse = getinverse)
 }
 
 
-## Write a short comment describing this function
-
+## Computes the inverse of the special "matrix" returned by makeCacheMatrix
+## f the inverse has already been calculated (and the matrix has not changed), 
+## retrieve the inverse from the cache.
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  m <- x$getinverse()
+  if(!is.null(m)) {
+    message("getting cached data")
+    return(m)
+  }
+  data <- x$get()
+  m <- solve(data, ...)
+  x$setinverse(m)
+  m
 }