diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..d144774c387 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,35 @@
-## Put comments here that give an overall description of what your
-## functions do
-
-## Write a short comment describing this function
+## Create an object that contains a matrix
+## and caches its inverse
+## Use: 
+## to create object
+## cmatrix <- makeCacheMatrix(matrix)  
+## to invert
+## inverse <- cacheSolve(cmatrix)
 
+## Create an object that is a matrix caching its inverse
 makeCacheMatrix <- function(x = matrix()) {
-
+  inv <- NULL
+  set <- function(y) {
+    x <<- y
+    inv <<- NULL
+  }
+  get <- function() x
+  setinv <- function(newinv) inv <<- newinv
+  getinv <- function() inv
+  
+  list(set = set, get = get, setinv = setinv, getinv = getinv)
 }
 
 
-## Write a short comment describing this function
-
+## Return a matrix that is the inverse of 'x'
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  inv <- x$getinv()
+  if(!is.null(inv)) {
+    inv
+  } else {
+    data <- x$get()
+    inv = solve(data, ...)
+    x$setinv(inv)
+    inv
+  }
 }