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Q&A-KCSE Computer Studies Paper 1

Distinguish between real time processing and interactive processing

  • Real-time processing is where data is processed as it is received and the output is made available immediately to influence the ongoing activity
  • Interactive processing is computer processing in which the user can modify the operations appropriately while observing results at critical steps

Describe the difference between distributed and sequential processing on how they process instructions

  • Sequential processing occurs in the order that the tasks are received while distributed processing where more than one computer or CPU is used to run specific programs.

During data entry, Anne typed the letter S instead of 5. What type of error is this?                                                                                                                                            (1mark)

        Misreading error

List Three file organisation methods in a computer

  • Sequential
  • Random
  • Serial
  • Indexed-sequential

State advantages of batch processing

  • once instructions are given, the processing runs automatically hence requiring little supervision
  • tasks are processed as a group hence reducing the cost
  • It is faster since the since runs automatically
  • there is increased output since the processor works without any interruption

State four threats that compromise data integrity and state ways that can be used to minimise these threats

State four threats that compromise data integrity

  • Human error
  • natural disaster
  • data transmission errors
  • software bugs

How threats to data integrity can be minimised:

  • Backup data preferably on an external storage media
  • control access to data by enforcing security measures
  • design user interfaces that minimise chances of invalid data entry
  • using error detection and correction software when transmitting data over the network
  • using devices that directly capture data from the source such as bar code readers, digtal cameras, and optical character readers

 

State what is meant by each of the following modes of data  processing

(i) Batch processing.
(ii) Real-time processing.
(iii) Online processing.
(iv) Off-line processing.

(i) Jobs collected together for processing at a later time
(ii) Output produced quickly enough to affect the next input
(iii) User has direct contact with the processor
(iv) User cannot communicate directly with the processor

Give two reasons why hexadecimal is often used instead of binary in computer
science.

  • hexadecimal is easier (for humans) to read (than binary);
  • numbers are displayed in a more compact way (in hexadecimal than in binary);
  • it is quicker to type in (hexadecimal numbers than binary numbers);
  • it reduces the risk of typing errors (in hexadecimal numbers than binary numbers);

A computer operates as a binary digital device. Explain why binary is used to represent computer data.

  • Binary can represent two states because computer circuits use transistors, which can either be on or off

A car park uses a number plate recognition system. Identify the reason why unsigned integers should be used to record the number of cars entering and leaving the car park, rather than signed integers

  • Unsigned integers store more positive values

A sound engineer is recording a singer. Describe why the sound must be converted to a digital format before it can be stored on a computer system

  • Computer systems use binary/ones and zeros/voltage on or off;
  • Sound is analogue/continuous;
  • Computers use digital data/discrete values

Elucidate the fact that zero can only be represented in one way in twos complement and in two ways in ones complement

Taking a four-digit 0  binary number i.e (0000)2

In ones complement this is  1111

In twos complement this becomes 1111+1= 0000

So, It is clear that 0 and negative zero is the same in twos complement while in ones complement they are two different values

Why is 2's complement preferred over 1's complement?

  • two's complement has only one value for zero

(a)Explain why programmers prefer to represent instruction in hexadecimal rather than in binary

  • A larger number of values can be represented using fewer characters.
  • the shorter length and more characters make the pattern easier to read and understand
  • recognisable character codes can be used for debugging

(b) Give two other uses of hexadecimal

  • HMTL color codes representing RGB spectrum in the web development
  • representation of MAC and IP addresses allowing a larger combination of unique addresses

(a)Explain why programmers prefer to represent instruction in hexadecimal rather than in binary

  • A larger number of values can be represented using fewer characters.
  • the shorter length and more characters make the pattern easier to read and understand
  • recognisable character codes can be used for debugging

(b) Give two other uses of hexadecimal

  • HMTL color codes representing RGB spectrum in the web development
  • representation of MAC and IP addresses allowing a larger combination of unique addresses

Explain three ways a computer can store negative numbers                                            (3 marks)

Prefixing an extra sign bit- A negative number is representes by prefixing a digit 1 to the number

Ones complement- This is flipping the binary equivalent of the number

Twos complement- this involves getting the ones complement and then adding a 1