IGCSE COMPUTER SCIENCE - UNIT #5
EXAM QUESTIONS WITH COMPLETE
ANSWERS
Types of input devices - Answer-Input devices transfer data from the source in the
outside world to the computer. For example, scanners, barcode readers, digital
cameras.
UPC-A systems - Answer-This uses long guard bars to show the start and end of the
barcode and also central guard bars to distinguish left uniquely from right.
How does a scanner read a barcode? - Answer-The scanner shines a light at the
barcode, light is reflected back to the scanner, photoelectric cells in the scanner detect
the light, the pattern of lines is converted to digital values
A microprocessor interprets the data.
2D scanners - Answer-These are used to convert a hard/paper copy document or
photograph into a computer-readable format.
Operation of a 3D laser scanner - Answer-A moving laser projects a beam of laser light
onto the object, two sensor cameras continuously record the changing distance and
shape of the laser line in three dimensions, the shape of the object appears as millions
of points known as a "point cloud" on the computer monitor as the laser moves around
the object.
Digital cameras - Answer-A camera works in much the same way as a scanner, when a
digital camera captures an image it breaks up what it sees through its lens into a grid of
pixels.
How do keyboards and keypads work? - Answer-When a key is pressed, the small bar
under the key pushes through a small hole and makes contact with a conducting
membrane.
A mouse - Answer-A mechanical mouse uses a rubber ball underneath the mouse
which moves around
on a hard surface and a optical mouse uses a red LED and a sensor to determine the
movement of the mouse.
Resistive touchscreens - Answer-Resistive touchscreens are made up of a layer of
conductive polyester and a layer of conductive glass, when the screen is gently pressed
by a finger, the two conducting layers make contact and complete a circuit.
EXAM QUESTIONS WITH COMPLETE
ANSWERS
Types of input devices - Answer-Input devices transfer data from the source in the
outside world to the computer. For example, scanners, barcode readers, digital
cameras.
UPC-A systems - Answer-This uses long guard bars to show the start and end of the
barcode and also central guard bars to distinguish left uniquely from right.
How does a scanner read a barcode? - Answer-The scanner shines a light at the
barcode, light is reflected back to the scanner, photoelectric cells in the scanner detect
the light, the pattern of lines is converted to digital values
A microprocessor interprets the data.
2D scanners - Answer-These are used to convert a hard/paper copy document or
photograph into a computer-readable format.
Operation of a 3D laser scanner - Answer-A moving laser projects a beam of laser light
onto the object, two sensor cameras continuously record the changing distance and
shape of the laser line in three dimensions, the shape of the object appears as millions
of points known as a "point cloud" on the computer monitor as the laser moves around
the object.
Digital cameras - Answer-A camera works in much the same way as a scanner, when a
digital camera captures an image it breaks up what it sees through its lens into a grid of
pixels.
How do keyboards and keypads work? - Answer-When a key is pressed, the small bar
under the key pushes through a small hole and makes contact with a conducting
membrane.
A mouse - Answer-A mechanical mouse uses a rubber ball underneath the mouse
which moves around
on a hard surface and a optical mouse uses a red LED and a sensor to determine the
movement of the mouse.
Resistive touchscreens - Answer-Resistive touchscreens are made up of a layer of
conductive polyester and a layer of conductive glass, when the screen is gently pressed
by a finger, the two conducting layers make contact and complete a circuit.
