diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..465df594041 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,46 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Calculate inverse of a matrix is a time-consuming computation. 
+## We provide a cacheMatrix implementation here by caching the inverse
+##  calculation result of the matrix. If the contents of a matrix are 
+##  not changing, we will access the cached inverse directly rather 
+##  than re-calculate the inverse once again.
 
-## Write a short comment describing this function
+## makeCacheMatrix creates a special "matrix", which is really a list 
+##  containing a function to
+##  1. set the value of the matrix
+##  2. get the value of the matrix
+##  3. set the value of the inverse
+##  4. get the value of the inverse
 
 makeCacheMatrix <- function(x = matrix()) {
-
+  i <- NULL
+  set <- function(y) {
+    x <<- y
+    i <<- NULL
+  }  
+  get <- function() x
+  setinverse <- function(inverse) i <<- inverse
+  getinverse <- function() i
+  list(set=set, get=get,
+       setinverse = setinverse,
+       getinverse = getinverse)
 }
 
 
-## Write a short comment describing this function
+## The following function calculates the inverse of the special "matrix" 
+##  created with the above function. However, it first checks to see if the 
+##  inverse has already been calculated. If so, it gets the inverse from the
+##  cache and skips the computation. Otherwise, it calculates the inverse of 
+##  the data and sets the value of the inverse in the cache via the setinverse
+##  function.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+  i <- x$getinverse()
+  if (!is.null(i)) {
+    message("getting cached data")
+    return(i)
+  }
+  data <- x$get()
+  i <- solve(data, ...)
+  x$setinverse(i)
+  i
 }