Exercise on Input and Output


a)   What do we understand by the term Peripheral? Give two examples.

b)  Devices can be categorized as input, output or input/output devices. In the following table you are required to write the type near each device.

Cordless mouse




Touch screen






Light pen


Bar-code reader



c)   What do these abbreviations stand for?

i)           OMR

ii)          OCR

iii)        MICR


Old computers were only capable of displaying 16 colours. How many bits of data does the computer need to be able to represent 16 colours?


This question is an example of how binary signals can be used to control a mechanical device. This system uses a five-bit signal to operate the various functions of a washing machine. Which signal is passed to the machine depends on the current progress of the program selected by the user.

4th bit

3rd bit

2nd bit

1st bit

0th bit


Spin dryer mode

Wash mode

Pump outlet valve

Water inlet valve

Off (0)

On (1)

Stop (0)

Active (1)

Stop (0)

Active (1)

Closed (0)

Open (1)

Closed (0)

Open (1)


a)  What is the name given to a computing device that integrates with machines such as the one demonstrated above?

b)  What happens when the signal that corresponds to the decimal number 21 is passed to the machine? Show your working.

c)   What signal does the system need to pass if the next step of the washing process involves spin-drying the load and removing excess water from the machine? Show your working.


This question is about validation and verification measures.

a)   Distinguish between validation and verification.

b)  Using arrows match the following measures with the appropriate descriptions.

1. Duplicate check


A. Checks that a field is not left emptied.

2. Layout check


B. Checks that the data entered fits within minimum and maximum limits.

3. length check


C. Checks that the data entered adheres to a particular structure such as #######L.

4. Presence check


D. Checks that the data entered doesn’t already exist in the database.

5. Range check


E. Checks that the data entered is a number when a number is expected.

6. Type check


F. Checks that the data entered has the necessary amount of characters.