Subsituting in the entire file

vim-commands

@@ -465,3 +465,41 @@ Line mode:
 
 	Pressing "<register-name> with "y" command and then using "/<string-pattern>" will leads to
 	yanking(copying) from the current cursor position to the next occurance of the <string-pattern>.
+
+
+	@ Command : [range]s/<old>/<new>/[flag]  (Its a line command)
+		      ^			   ^
+		      |			   |
+		    optional		optional
+
+
+	 What does it do?
+	
+	 It replace the occurance of old string to new string over the range
+	 in the file.
+
+	 [flag]
+	
+	 * g : It represent to replace all the occurance of <old> to <new> in
+	       current line where the cursor is present.
+
+	 
+	 [range]
+
+	 Define the range of this command. Could be single line, multiple line
+	 and even all the lines in the file, etc.
+
+	 * <line-number> : On which line number this command to be executed.
+
+	 * <start-line-number>,<end-line-number> : From the starting line number
+						   to the ending line number to 
+						   to execute the command.
+
+		For ex:
+			:1s/<old>/<new>/g
+
+			It will replace <old> with <new> in the entire line of line number 1.
+
+			:1,5s/<old>/<new>/g
+
+			It will do the same form line number 1 to 5.