Computer Science Paper 1
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What does a check digit correct (x2)
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Single digit errors, Phonetic errors
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Explain to Kamil why it is better to use DVD-RAM rather than DVD+RW or DVD-RW.
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1) direct access because of concentric tracks 2) can read and write at the same time because it has a read/write head
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The clock alarm has been set at 08:00. Describe the actions of the microprocessor which enable the alarm to sound at 08:00
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1) microprocessor compares present time with stored time 2) sends signal to sound alarm
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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?
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1) re-reading the byte that was sent 2) request that the byte is resent
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Even parity check
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last number should be 1 to pass the check, otherwise fail.
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Odd parity check
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last number should be 0 to pass the check, otherwise fail.
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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.
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1) Temperature sensor 2) Oxygen sensor
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What safeguards are needed to stop the fish tank temperature rising too high?
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thermometer, alarm sound
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MAC address
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unique ID for a network interface card
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what does Internet Server do
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computer that responds to requests to provide information and services over the Internet
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http
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defines how messages are transmitted and formatted over the Internet
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Ahmed sees the message \"Set your browser to accept cookies\". Explain why some websites make this request.
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1) to enable logon information to be kept on his computer 2) to provide pages customised for Ahmed the next time he logs on
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Computer memories are measured in terms of the number of bytes. What is meant by the term byte?
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it is a unit of data
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The number of bytes in a Gigabyte can be written as 2x What is the value of x?
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30
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Flash memories and CD-RWs are used as backing media for computers. Give two differences between these two media.
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Flash memory plugs directly into the USB port. CD-RW is Optical Media. CD-RW has slower access speed - flash memory is faster
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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.
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RAM
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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.
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interrupt signal
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The quick brown fox jumps over the lazy dog. Decode this cypher text message: Agbbm Pmubq
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Hello World
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What is meant by SSL?
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Secure Socket Layer
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How does SSL keep the copy of the key secret during transmission?
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the key itself is encrypted using strong encryption
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Give one benefit of writing code in a high-level language.
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easier to understand for programmer/closer to English
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Give one benefit of writing code in a low-level language.
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can be written to run faster
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High-level languages can be compiled or interpreted. Give two differences between a compiler and an interpreter.
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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
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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
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FA97
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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.
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1) easier to identify values 2) easier to spot errors
