State the characteristics of each of the following network topologies (KCSE COMPUTER STUDIES 2021 )

i) Mesh Topology  (2mks)

• a host/node is connected to one or multiple hosts
• a   host/node in point to point connection with every other host or a few hosts
• hosts/nodes in mesh topology also work as relays for other hosts which do not have point-to-point links

(ii) Ring Topology (2mks)

• each host/node connects exactly to two other hosts
• data travels around the ring in one direction through all intermediate hosts
• failure of any host results in the failure of the whole ring

– fact finding
– feasibility study
– analysis
– design
– testing
– documentation
– implementation/changeover/installation
– evaluation
– maintenance

Job scheduling/Process scheduling                                                                                              (2mks)

• Operating systems allocate tasks/processes/jobs to the CPU using priority and FIFO principle

 Memory management                                                                                                                  (2mks)

• OS allocates and de-allocates memory spaces to processes loaded into the RAM
• Swaps processes between main memory and virtual memory created in the secondary storage

• Unfamiliar graphics or quizzical messages appear on the screen
• Programs taking longer than usual to load
• Less memory allowance than usual
• Unusual error messages occurring more frequently

• Allows creation and management of user accounts
• Helps in troubleshooting of the network
• controls access to network resources
• Provides communication services
• configures network resources
•  

A PAN exist around a single person whereas a LAN covers a larger area

• Developing training materials
• Training computer users
• Conducting ICT examinations
• Managing the learning and examination process
• Developing guidelines for using the computer lab
• Planning the course content
•  

• An instruction is retrieved from the memory
• The instruction is decoded
• The instruction is executed
• the program counter is incremented

• A denial of service strategy usually works flooding the target host or network with traffic until the target can’t respond or crashes. The targeted systems operations are affected when users are unable to access information systems and or network services

 the trial version of software for a limited time/number of uses with limited features  free of charge

If a full version is required need to pay a fee/sign up

When the trial is over user is asked to pay/sign up

Protected by copyright

Type of software licence
 

The booting process is the sequence of events that occur when a computer is turned on or restarted. It involves a series of steps that allow the computer's operating system to initialize and become functional. Here's a simplified explanation of what happens during the booting process:

1. Power-On Self-Test (POST): When the computer is powered on, the first thing it does is perform a Power-On Self-Test. During this step, the computer's hardware components, such as the CPU, memory, and storage devices, are checked for proper functioning. The POST verifies that all essential hardware components are present and operational.

2. Bootloader: Once the POST is completed, the computer looks for the bootloader. The bootloader is a small program stored in the computer's firmware or on the bootable device (such as the hard drive or a USB drive). It is responsible for loading the operating system.

3. Loading the Operating System: The bootloader locates the operating system's files and initiates the loading process. It may display a boot menu allowing the user to choose the operating system if multiple options are available. The selected operating system's core files are loaded into the computer's memory.

4. Kernel Initialization: The operating system's kernel, which is the central component responsible for managing system resources, is initialized. The kernel sets up essential components such as device drivers, memory management, and process management.

5. System Initialization: After the kernel is initialized, the operating system proceeds with system initialization. During this stage, various system services and processes are started, and hardware devices are initialized and configured. The operating system loads essential system files and prepares the environment for user interaction.

6. Login/Graphical Interface: Once the system initialization is complete, the user is presented with a login prompt or a graphical user interface (GUI). The user can then log in with their credentials or interact with the GUI to access the computer's functionalities.

• It requires that a foreign key must have a matching primary key or it must be null

(a) State two items of data that are stored on the barcode.

• check digit
• product number/item number/code
• country of origin
• manufacturers number/code
• weight
• price

(b) Describe how the computer system checks that the barcode has been read correctly.

• check digit calculation is performed on the check digit, remainder = 0 if the barcode has been read correctly
• weights and modulus 11 and use remainder
• or subtractions and addition and use answer

(c) State the type of file access that is used to get the price from the central computer.

• random/direct/online

(d) Explain how the system updates the file when an item has been sold.

• search file/master file using barcode number/product code and decrease number in stock/increase quantity sold

• It refers to a computer that controls other computers in a network and monitors user's access to the shared resources.

A variable is a memory location used to store a value

• problem recognition involves the system analyst identifying and accepting the existence of a problem in the current system
• problem definition involves the analyst studying the system to understand its operations and shortcomings

A parameter represents additional information that  a function requires to perform its task. Each parameter required by a function is specified in the function header

An argument the value supplied in the function call. When the function is called, the argument value is passed into the function parameter so that the function can perform its task

• Hierarchical model  - Records in the database can be related to one parent only but can have more children records
• Network database model - a child record can be linked to  multiple parent records
• Relational database model - organizes data into tables that can be linked or related based on data common to each.

• Guided media uses cables to connect to computers whereas unguided media uses waves.

17. a) i) Explain the term search as used in the Internet.                                            [2]

A web based application that locates items or information from the World Wide Web

ii) Peter intends to download a movie from the Internet. State the three factors that may determine the total time taken to complete the download.                                           [3]

• Size of the video/format
• The bandwidth of the media/speed of network/network traffic
• Type of browser software
• Background activities running in the computer
• Restrictions enforced in the computer/firewall/antivirus
• Speed of the computer/CPU speed
• Size of RAM

b) Wakulima online is an organization that runs a web based system for assisting farmers to obtain market for their produce. State four technological reasons that may cause a farmer not to access the organization’s system.                                                                                  [4]

• Poor network/lack of connection
• Software failure in the system

• Hardware failure
• Lack of access rights
• System overload/hanging
• Lack of skills/disability/illiteracy
• Lack of power supply

c) Explain a situation when each of the following Desktop Publishing program features may be used when creating a publication:

i. Cropping                                                                                                               [2]

Applies to graphics – used to trim/remove/hide some portions in the graphics

ii. Transparency                                                                                                         [2]

Used to make background of a graphic to be clear/visible

d. List two areas where infrared waves are used in data communication.                             [2]

18. a) List four activities of the planning stage of systems development.                             Ignore this question, marks redistributed elsewhere

b) Explain a circumstance when each of the following feasibility studies are carried out during systems development.

i. Technical                                                                                                               [3]

Done to determine whether technology exists to support the proposed solution

ii. Economic                                                                                                              [3]

Done to determine whether the proposed solution is economically viable

iii. Schedule                                                                                                               [3]

Done to determine whether the proposed system can be done within an acceptable time.

c) Table 1 and Table 2 are related tables in a database. Use them to answer the questions that follow.

Table 1

Table 2

i. Identify the appropriate primary key for each table.                    [2]

Table 1 – Dept code, Student Registration No

ii. Explain two benefits of enforcing referential integrity in the database. [4]

• No record can be added in Table 2 if its corresponding record in Table 1 does not exist
• No record in Table 1 can be deleted without first deleting the corresponding record in Table 2
• Reduces data redundancies/ensures integrity
• Prevents deletion of related table

19. a) Describe each of the following validation checks as used in data processing.

i. Preserve check                                                                                                      [2]

Ignore this question, marks redistributed elsewhere

ii. Data type check                                                                                                    [2]

Ensure correct type of data is entered for the field

iii. Check digit                                                                                                           [2]

This is a number added/calculated by the computer to a binary number. The check digit ensures correct transmission of the binary number.

b. Write each of the following abbreviations in full:

i) BCD                                                                                                                                    [1½]

Binary Coded Decimal

ii) EBCD                                                                                                                                 [

This question was thrown out and marks redistributed elsewhere

iii) ASCII                                                                                                                    [1½]

American Standard Code for Information Interchange

c) Using 10-bits binary number system, perform the following decimal operation using two’s complement.                                                                                                                                   [6]

12910 - 12810

+129 = 00 1000 0001

128 = 00 1000 0000

-128 = 11 0111 1111 (ones complement)

                            +1

          11 1000 0000 (Twos complement)

129- 128

     00 1000 0001

+ 11 1000 0000

 100 0000 0001

Hence = 00 0000 00012 or 12 (the overflow bit is ignored)