Fundamentals of Computer Systems

Question 1

Describe how data is written to and read from a CD-R disk.

Answer 1

• To write, a high powered / high frequency laser makes sections less reflective / burns a pit.
• To read, a low powered laser is used to read data back from the disk.
• The difference between reflective and non-reflective parts / pits and lands indicates the 1s and 0s.

Question 2

Describe the principles of operation of both the reader and the RFID tag in and RFID system.

Answer 2

• RFID reader transmits a signal / emits electro-magnetic field.
• Signal activates / induces current in the RFID tag.
• RFID tag transmits data (by radio wave).

Question 3

Identify the differences between CD-ROM and hard disk drive storage.

Answer 3

• Hard disk drive uses magnetic media, CD-ROM is an optical media
• Hard disk drive uses magnetic induction (to read data), CD-ROM uses a laser (and sensor)
• Hard disk drive is a read / write medium, CD-ROM is read only
• Hard disk drive can be damaged by exposure to magnetic field, CD-ROM cannot
• CD-ROM can be scratched, hard disk drive cannot
• Hard disk drive can transfer / access data faster than a CD-ROM

Question 4

Describe the principles of operation of a laser printer.

Answer 4

• Bitmap of image built in memory from page description.
• Charge applied to (photosensitive) drum.
• Mirror is used to direct laser beam at the drum.
• Where laser strikes drum charge is reversed.
• Charge is applied to toner which sticks to drum based on charge.
• Paper passed over drum and toner transfers to it using a positively charged transfer roller.
• Heater fuses toner onto paper.
• For colour printing four different colour toners.

Question 5

Describe the difference between application software and system software.

Answer 5

Application Software: Performs user-oriented tasks.

System Software: Software used in the management of a computer system that abstract the user from how the computer works.

Question 6

Describe the role of the control unit.

Answer 6

• To control operation of fetch-execute cycle.
• Controls fetching / loading / storing operations.
• Determines the type of an instruction.
• To synchronise operation of processor.
• To send control signals / commands to other components.
• To control the transfer of data between registers.
• To handle interrupts.

Question 7

Describe:

• What cache memory is.
• What cache memory is used for.
• How increasing the amount of cache memory can improve the performance of a processor.

Answer 7

• Memory located on the processor.
• To store most frequently/recently used pre-fetched instructions/data.
• More instructions/data can be stored in the cache; Instructions/data stored in cache can be accessed more quickly than instructions/data in main memory; fewer fetches from main memory will be required.