update read me

Author: Alex Gaetano Padula

README.md

@@ -1,11 +1,11 @@
 # GO BTree
-A fast, simple persistent BTree implementation in Go.
+A fast, simple disk based BTree implementation in Go.
 
 https://pkg.go.dev/github.com/guycipher/btree
 
 ## Features
 - Easy to use API with `Put`, `Get`, `Delete`, `Remove`, `Iterator`, `Range` methods
-- Disk based storage
+- Disk based storage with underlying pager
 - Supports keys with multiple values
 - Supports large keys and values
 
@@ -31,7 +31,7 @@ import "github.com/guycipher/btree"
 
 You can use the ``Open`` method to open an existing btree or create a new one.
 You can specify the file, permission and T(degree)
-```
+```go
 // name of the file, flags, file mode, T(degree)
 bt, err := btree.Open("btree.db", os.O_CREATE|os.O_RDWR, 0644, 3)
 if err != nil {
@@ -42,7 +42,7 @@ if err != nil {
 ### Inserting a key-value pair
 
 You can insert a value into a key using the ``Put`` method.  Keys can store many values.
-```
+```go
 err := bt.Put([]byte("key"), []byte("value"))
 if err != nil {
 ..
@@ -52,17 +52,62 @@ if err != nil {
 ### Getting a value
 
 To get a value you can you the ``Get`` method.  The get method will return all the keys values.
-```
+```go
 values, err := bt.Get([]byte("key"))
 if err != nil {
 ..
 }
 ```
 
+#### NGet
+To get all keys not equal to the key you can use the ``NGet`` method.
+```go
+keys, err := bt.NGet([]byte("key"))
+if err != nil {
+..
+}
+```
+
+### GreaterThan
+To get all keys greater than the key you can use the ``GreaterThan`` method.
+```go
+keys, err := bt.GreaterThan([]byte("key"))
+if err != nil {
+..
+}
+```
+
+### GreaterThanEq
+To get all keys greater than or equal to the key you can use the ``GreaterThanEq`` method.
+```go
+keys, err := bt.GreaterThanEq([]byte("key"))
+if err != nil {
+..
+}
+```
+
+### LessThan
+To get all keys less than the key you can use the ``LessThan`` method.
+```go
+keys, err := bt.LessThan([]byte("key"))
+if err != nil {
+..
+}
+```
+
+### LessThanEq
+To get all keys less than or equal to the key you can use the ``LessThanEq`` method.
+```go
+keys, err := bt.LessThanEq([]byte("key"))
+if err != nil {
+..
+}
+```
+
 ### Deleting a key
 
 To delete a key and all of it's values you can use the ``Delete`` method.
-```
+```go
 err := bt.Delete([]byte("key"))
 if err != nil {
 ..
@@ -72,18 +117,18 @@ if err != nil {
 ### Removing a value within key
 
 To remove a value from a key you can use the ``Remove`` method.
-```
+```go
 err := bt.Remove([]byte("key"), []byte("value"))
 if err != nil {
 ..
 }
 ```
 
-### Iterator
+### Key Iterator
 
 The iterator is used to iterate over values of a key
 
-```
+```go
 iterator := key.Iterator()
 
 for {
@@ -104,18 +149,28 @@ value3
 ```
 
 ### Range query
-```
+Get all keys between key1 and key3
+```go
 keys, err := bt.Range([]byte("key1"), []byte("key3"))
 if err != nil {
 ..
 }
 ```
 
+### Not Range query
+Get all keys not between key1 and key3
+```go
+keys, err := bt.NRange([]byte("key1"), []byte("key3"))
+if err != nil {
+..
+}
+```
+
 ### Closing the BTree
 
 You can close the BTree by calling the Close function.
-
-```
+This will close the underlying file and free up resources.
+```go
 err := bt.Close()
 if err != nil {
 ..