How many times have you kept your book open with your eyes fixed on it and not read a single word? This happens because the Control Unit of your brain does not allow your eyes to provide an input at a given point of time.
A Control Unit is that part of the computer, which makes the ALU and Memory work in synchronization with the data. It is a part of the central processing unit which directs the sequence of operations, interprets coded instructions and sees to the execution of program instructions. In order to process instructions sequentially, the CU goes through the following steps:
1. Retrieves an instruction from the processor memory.
2. Determines the action to be taken, on being requested.
3. Directs the CPU to perform operations.
4. Determines whether the operations\ was carried out properly or not.
5. Displays an error message to the user if the operation was not carried out properly - through the output device.
6. Stores the result in memory for further processing, if error free.
7. Determines the location of the next instruction.