Computer Science Paper 1

question

What does a check digit correct (x2)
answer

Single digit errors, Phonetic errors
question

Explain to Kamil why it is better to use DVD-RAM rather than DVD+RW or DVD-RW.
answer

1) direct access because of concentric tracks 2) can read and write at the same time because it has a read/write head
question

The clock alarm has been set at 08:00. Describe the actions of the microprocessor which enable the alarm to sound at 08:00
answer

1) microprocessor compares present time with stored time 2) sends signal to sound alarm
question

Bytes of data transferred using a serial cable are checked for errors at the receiving end using an even parity check. How can any errors be corrected?
answer

1) re-reading the byte that was sent 2) request that the byte is resent
question

Even parity check
answer

last number should be 1 to pass the check, otherwise fail.
question

Odd parity check
answer

last number should be 0 to pass the check, otherwise fail.
question

The conditions in a fish tank are being controlled using sensors and a microprocessor. To keep the fish healthy, the temperature must be at 25°C and the oxygen content needs to be 20 ppm (parts per million). The tank contains a heater and an oxygen inlet controlled by a valve. Name the two sensors used in this application.
answer

1) Temperature sensor 2) Oxygen sensor
question

What safeguards are needed to stop the fish tank temperature rising too high?
answer

thermometer, alarm sound
question

MAC address
answer

unique ID for a network interface card
question

what does Internet Server do
answer

computer that responds to requests to provide information and services over the Internet
question

http
answer

defines how messages are transmitted and formatted over the Internet
question

Ahmed sees the message \”Set your browser to accept cookies\”. Explain why some websites make this request.
answer

1) to enable logon information to be kept on his computer 2) to provide pages customised for Ahmed the next time he logs on
question

Computer memories are measured in terms of the number of bytes. What is meant by the term byte?
answer

it is a unit of data
question

The number of bytes in a Gigabyte can be written as 2x What is the value of x?
answer

30
question

Flash memories and CD-RWs are used as backing media for computers. Give two differences between these two media.
answer

Flash memory plugs directly into the USB port. CD-RW is Optical Media. CD-RW has slower access speed – flash memory is faster
question

Andrew sends a large document to a printer. State the name for the area of memory used to store temporarily the data being sent to the printer.
answer

RAM
question

The printer runs out of paper during the printing job. A signal is sent back to the computer to stop temporarily its current task. Name this type of signal.
answer

interrupt signal
question

The quick brown fox jumps over the lazy dog. Decode this cypher text message: Agbbm Pmubq
answer

Hello World
question

What is meant by SSL?
answer

Secure Socket Layer
question

How does SSL keep the copy of the key secret during transmission?
answer

the key itself is encrypted using strong encryption
question

Give one benefit of writing code in a high-level language.
answer

easier to understand for programmer/closer to English
question

Give one benefit of writing code in a low-level language.
answer

can be written to run faster
question

High-level languages can be compiled or interpreted. Give two differences between a compiler and an interpreter.
answer

1) compiler translates whole program in one go / interpreter translates and executes line at a time 2) compiler produces list of all errors / interpreter produces error message each time an error is encountered
question

The following machine code instruction is stored in a location of main memory: 1 1 1 1 1 0 1 0 1 0 0 1 0 1 1 1
answer

FA97
question

Explain why a programmer would prefer to see the contents of the locations displayed as hexadecimal rather than binary, when debugging his program that reads the key presses.
answer

1) easier to identify values 2) easier to spot errors

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