diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..67c4e1dd387 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,54 @@
-## Put comments here that give an overall description of what your
-## functions do
+## This function returns the inverse matrix of a nonsingular matrix specified
+## by users.
 
-## Write a short comment describing this function
+## makeCacheMatrix returns a function list that would be used in cacheSolve
 
 makeCacheMatrix <- function(x = matrix()) {
-
+        
+        ## initialize an object "m", which will be used to store inverse matrix
+        m <-NULL
+       
+        ## assign the input into "x", and also initialize the "m".
+        set <-function(y){
+                x <- y
+                m <- NULL
+        }
+        
+        get <- function() x             ## retrives the matrix stored in "x"
+        
+        setInv <- function(inv) m<<-inv     ## store the input into "m"
+        
+        getInv <- function() m              ## return the value of "m"
+        
+        ## combine the four functions into a list variable as an output
+        list(set = set, get = get,
+                 setInv = setInv,
+                 getInv = getInv)
+        
 }
 
 
-## Write a short comment describing this function
+## cacheSolve function is for retriving the cache if it exist, or create one
+## and store the inverse matrix in it if cache does not exist.
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
+    
+        m<- x$getInv()
+        
+        ## if "m" has a value in it, return this value (the inverse matrix)
+        ## and exit the function, otherwise jump to the next command.
+        if(!is.null(m)) {
+                message("getting cached inverse matrix")
+                return(m)
+        }
+        
+        ## if "m" is null, calculate the inverse of original matrix using
+        ## solve function.
+        data <- x$get()
+        m <- solve(data,...)
+        
+        ## store the result in "m", and return the value of "m", 
+        ## which is the inverse of "x"
+        x$setInv(m)
+        m
 }