diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..c74e4879431 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,35 @@
-## Put comments here that give an overall description of what your
-## functions do
+## A pair of functions that cache the inverse of a matrix.
 
-## Write a short comment describing this function
+## This function creates a special "matrix" object that can cache its inverse.
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  inv <- NULL
+  set <- function(y) {
+    x <<- y
+    inv <<- NULL
+  }
+  get <- function() x
+  setinv <- function(inverse) inv <<- inverse
+  getinv <- function() inv
+  list(set = set, get = get,
+       setinv = setinv,
+       getinv = getinv)
 }
 
 
-## Write a short comment describing this function
+## This function computes the inverse of the special "matrix" returned by
+## makeCacheMatrix above. If the inverse has already been calculated (and the
+## matrix has not changed), then cacheSolve retrieves the inverse from the
+## cache.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  inv <- x$getinv()
+  if(!is.null(inv)) {
+    message("Getting cached data.")
+    return(inv)
+  }
+  data <- x$get()
+  inv <- solve(data, ...)
+  x$setinv(inv)
+  inv
 }