WAEC SSCE - Computer Studies - 2018

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The term used for the conversion of readable data to unreadable codes in order to prevent unauthorized access is called encryption. Encryption is a process of converting plain text into a coded form called ciphertext that can only be deciphered with the right key. The idea behind encryption is to make it difficult for unauthorized individuals to access or understand the data. This helps to ensure the confidentiality and security of the information. In simple terms, encryption helps to protect sensitive information from being seen by anyone other than those who are authorized to view it.

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The process of restarting a computer system is commonly referred to as a "reboot" or a "restart." This involves shutting down the system and then starting it up again. There are two types of reboots: "cold boot" and "warm boot." A cold boot is when the computer is completely powered off and then started again. This is typically done by pressing the power button or shutting down the computer through the operating system and then restarting it. A warm boot, on the other hand, is when the computer is restarted without being powered off. This can be done by pressing the reset button on the computer or by using a keyboard shortcut, such as "Ctrl + Alt + Delete." "Hard booting" and "hot bathing" are not common terms used to describe the process of restarting a computer system.

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The three levels of programming languages are: low-level language, high-level language, and assembly language. A low-level language is a type of programming language that provides little or no abstraction from the computer's instruction set architecture. This means that the code written in a low-level language is closer to the machine language that a computer can understand. Examples of low-level languages include machine language and assembly language. A high-level language is a type of programming language that provides a higher level of abstraction from the computer's instruction set architecture. This means that the code written in a high-level language is further away from the machine language that a computer can understand, but is closer to the natural language that humans use. High-level languages are easier for humans to read, write, and understand. Examples of high-level languages include Java, C, and Pascal. Assembly language is a type of low-level programming language that provides a level of abstraction between machine language and high-level languages. Assembly language uses mnemonics (symbols) to represent the instructions that a computer can understand. The code written in assembly language is still close to the machine language, but is easier for humans to read and write than machine language.

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The system unit is the main part of a desktop computer that contains all the essential components needed for the computer to work. These components include the motherboard, central processing unit (CPU), and various other storage devices like hard drives or SSDs. Out of the options listed, the component that is not housed in the system unit is the plotter. A plotter is a printing device that is used to produce high-quality graphics and drawings, typically used in engineering and architectural designs. It is a separate device that connects to the computer and is not a part of the system unit. In summary, the system unit contains important components like the motherboard and CPU, but a plotter is not housed inside the system unit.

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The system unit houses components that are essential to the functioning of a computer. However, it does not include a plotter. A plotter is a type of large-format printer that is used to print high-quality images or technical drawings. It is not a component that is typically found inside a system unit. The other options listed (motherboard, floppy disk, and central processing unit) are all commonly found inside a system unit.

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The Doughnut chart does not display the X and Y axes. A Doughnut chart is a circular chart that is used to represent proportions and ratios. It is divided into segments that each represent a proportion of the whole. Unlike bar charts and X, Y graphs, doughnut charts do not have X and Y axes. The data is represented by the size and color of the segments in the chart.

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Out of the four options listed, the component that is not a network interconnecting device is a webcam. A webcam is a device that captures video and sends it to a computer, where it can be transmitted over the internet. However, it is not a device that interconnects networks; it simply sends information from one device to another. Hubs, modems, and routers, on the other hand, are devices that help connect and manage multiple devices on a network.

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The QBASIC keywords that do not include are "FIND B". This is because "FIND B" is not a valid QBASIC keyword. On the other hand, "LET C", "REM D", and "STOP" are valid QBASIC keywords. "LET" is used to assign a value to a variable, "REM" is used to add a comment in the code, and "STOP" is used to halt the execution of the program. It's important to note that QBASIC keywords are specific words that have a predefined meaning in the QBASIC programming language. Understanding these keywords is essential for writing correct and functional QBASIC programs.

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The speed of data transfer in a computer can be determined by two factors: bus speed and storage media. Bus speed refers to how fast data can travel between different components within a computer. It's like the speed limit on a highway; the higher the bus speed, the faster data can travel. Bus width, on the other hand, refers to how many bits of data can be transferred at once. It's like the number of lanes on a highway; the wider the bus, the more data can be transferred at once. Storage media, such as hard drives and solid-state drives, also play a role in data transfer speed. These devices have different read and write speeds, which determine how quickly data can be accessed and transferred. Protocols are also important for data transfer, as they dictate how data is transmitted and received. Different protocols have different speeds and efficiencies, and can impact the overall speed of data transfer. In summary, the speed of data transfer in a computer depends on both the bus speed and width, as well as the speed of the storage media and the protocols being used.

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The device that made use of beads and frames is called an Abacus. An abacus is a simple counting tool that consists of a wooden frame with parallel rods or wires running along its length. Beads or stones are strung on these rods or wires, and they can be moved back and forth to perform calculations. Abacuses were used in many ancient cultures, including China, Japan, and Egypt, and they are still used in some parts of the world today. They were particularly useful for merchants and traders who needed to perform quick calculations, and they were also used by scholars to teach mathematical concepts. To use an abacus, you move the beads along the rods to represent numbers. For example, if you wanted to represent the number 23, you would move two beads on the top row and three beads on the bottom row. You can then add, subtract, multiply, and divide by moving the beads in different ways. Overall, the abacus was a simple but effective device that played an important role in the development of mathematics and computing.

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"Valid data" is not a data type. Data types are categories of data that define what type of values a variable can hold, such as alphabetic characters, numbers, or a combination of both (alphanumeric). The term "valid data" refers to data that meets certain criteria, such as being within a specified range, having a certain format, or being free of errors. But it is not a type of data in the same sense as alphabetic, alphanumeric, or numeric data.

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A row in a database table is commonly referred to as a "record". A record represents a single instance of data within the table, and contains all the information related to a specific item or entity. For example, in a database table for a library, a record might represent a single book and its attributes, such as title, author, ISBN number, and publication date. Each attribute in the record is typically stored in a separate "field".

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Out of the four options given, CorelDraw, MS Access, and MS Word are general-purpose software, while "Editor" is not a specific software application. It could refer to a generic term for any software that allows users to edit or modify text, graphics, or other types of data. CorelDraw is a vector graphics editor that allows users to create and edit vector images and designs. It is widely used by graphic designers, illustrators, and artists to create logos, brochures, web graphics, and other types of visual content. MS Access is a database management system that allows users to store, organize, and manage large amounts of data. It provides a graphical user interface for creating tables, forms, reports, and queries, and is often used by businesses and organizations to manage customer data, sales records, and other types of information. MS Word is a word processing program that allows users to create, edit, and format text documents. It is widely used for creating letters, reports, resumes, and other types of written content. In summary, three out of the four programs mentioned (CorelDraw, MS Access, and MS Word) are general-purpose software, while "Editor" is not a specific application and could refer to any software that allows users to edit or modify data.

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The largest computer system in terms of processing power is a supercomputer. A supercomputer is a type of computer that is specifically designed to perform incredibly complex and demanding computational tasks faster and more efficiently than any other type of computer. Supercomputers use many processors working in parallel, as well as large amounts of high-speed memory and specialized hardware, to perform their tasks at incredibly high speeds. They are used for tasks such as weather forecasting, scientific simulations, and military applications, where the ability to process vast amounts of data and perform complex calculations is critical.

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The most important system software in a computer system is the Operating System (OS). The operating system acts as the intermediary between the computer hardware and the applications you use. It manages the resources of the computer such as memory and processing power, and it provides a platform for you to run your applications on. It also provides a user interface, such as a graphical desktop, to interact with the computer. In a very simple way, you can think of the operating system as the "brain" of the computer that controls all the important functions and makes sure everything runs smoothly.

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Data refers to raw facts or figures that are collected through various means such as observations, experiments, surveys, and measurements. It can be any type of information that can be stored and processed, including numbers, text, images, and sound. Raw data is unprocessed and lacks any structure or organization. It needs to be processed and analyzed to extract meaningful insights and useful information. For example, a list of sales figures is data, but the total revenue and average sales figures derived from it are processed information. Therefore, out of the given options, data can be defined as raw facts.

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One megabyte (MB) is equivalent to 1024 kilobytes (KB). To understand this, we first need to know that a byte is a unit of digital information that is made up of 8 bits. A bit is the smallest unit of digital information that can be stored or transmitted, and it can have a value of either 0 or 1. Now, a kilobyte (KB) is equal to 1024 bytes, and a megabyte (MB) is equal to 1024 kilobytes. So, one megabyte is equal to 1024 x 1024 = 1,048,576 bytes. It's important to note that there are two common interpretations of "mega" in the context of digital storage: the binary interpretation (2^20, or 1,048,576), and the decimal interpretation (10^6, or 1,000,000). The binary interpretation is used in most cases, including for measuring RAM and hard drive space. However, the decimal interpretation is sometimes used for measuring network data transfer rates. So, in short, one megabyte is equivalent to 1,048,576 bytes or 1024 kilobytes.

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I and III are data communication equipment. A scanner is a device that captures images from photographs or documents and converts them into digital data that can be processed by a computer. A modem (short for modulator-demodulator) is a device that converts digital data into analog signals for transmission over analog networks (such as telephone lines) and vice versa. Modems are used to connect computers to the internet. A hub is a networking device that allows multiple devices to be connected together and share network resources. A hub does not modify the data being transmitted, but simply repeats the same data to all connected devices. So, a scanner is used to convert physical images into digital data and a modem is used to convert digital data into analog signals for transmission over analog networks.

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The binary number system uses only two digits, 0 and 1, to represent all values. To convert a decimal number, such as 28, to binary, we can repeatedly divide the decimal number by 2 and keep track of the remainders. The binary representation of 28 is 11100. Here's how the conversion works: 28 ÷ 2 = 14 with a remainder of 0 14 ÷ 2 = 7 with a remainder of 0 7 ÷ 2 = 3 with a remainder of 1 3 ÷ 2 = 1 with a remainder of 1 1 ÷ 2 = 0 with a remainder of 1 So, the binary representation of 28 is 11100, with the rightmost digit being the least significant bit.

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The statement in QBASIC that is used to add data at the end of an existing sequential file is "APPEND".

When you open a sequential file for writing, by default, it starts writing from the beginning of the file and overwrites any existing data. However, if you want to add data to the end of the file, without deleting or overwriting the existing data, you can use the "APPEND" statement.

The "APPEND" statement opens the file for writing, but instead of overwriting the existing data, it positions the write pointer at the end of the file, allowing you to add new data to the file without affecting the existing data.

Here's an example of how to use the "APPEND" statement in QBASIC:

OPEN "my_file.txt" FOR APPEND AS #1
PRINT #1, "This is some new data added to the end of the file."
CLOSE #1

In this example, the "OPEN" statement opens the file "my_file.txt" for appending. The "PRINT" statement writes the new data to the end of the file, and the "CLOSE" statement closes the file.

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As a computer professional, my advice to the school would be to automate the system. Automating the system involves using computer software to process and compute the students' results. This would eliminate the need for manual calculations and reduce the time required to produce accurate results. With automation, the school can also easily store and retrieve student records, generate reports, and analyze data. It is a cost-effective and efficient solution that will help the school to produce reliable results in a timely manner. Closing down the school or increasing the number of staff or buying more calculators for staff would not solve the problem of time and accuracy of the result, and would only lead to more expenses without solving the underlying issue.

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The ASCII chart control characters use numeric codes ranging from 0 to 127. ASCII stands for American Standard Code for Information Interchange and is a system for representing characters (letters, numbers, symbols, etc.) as numbers. Control characters are special characters in the ASCII chart that are used to control the format or flow of data. These characters include things like line breaks, tabs, and other non-printing characters. The ASCII chart assigns a unique number to each character, and the control characters are assigned numbers between 0 and 127.

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The file that contains a historical record is called a "data file." This is because a data file stores information in a structured manner, often in rows and columns, and it can include historical data as well as current data. A data file can be used for various purposes such as record-keeping, analysis, and reporting. For example, a company might use a data file to store historical sales data for analysis and forecasting purposes. Similarly, a researcher might use a data file to store historical data related to a particular topic for analysis and interpretation. Therefore, the term "data file" accurately reflects the function and purpose of a file that contains historical records.

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The correct answer is a hyperlink. A hyperlink is an icon, graphic, or text in a document or webpage that when clicked on, takes you to another file or object, such as another webpage or a specific location in the same webpage. It acts as a bridge between different web pages and allows you to move from one page to another with a simple click. You can recognize a hyperlink by its underlined blue color and when you hover your mouse over it, the cursor turns into a hand symbol.

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The MS-Windows shortcut key to initiate warm booting is Ctrl+Alt+Del. This combination of keys is also known as the three-finger salute. When you press these keys together, it brings up the Windows Security screen, which gives you options to lock the computer, switch users, sign out, change a password, or open the Task Manager. In addition, this key combination can also be used to restart the computer. After pressing Ctrl+Alt+Del, click on the power icon in the lower right corner of the screen and select "Restart" from the menu. This will initiate a warm boot, which means the computer is restarted without going through a complete power cycle. Warm booting is useful when you want to restart your computer quickly without shutting it down completely. It is also helpful when you are experiencing some performance issues or errors that can be resolved by restarting the computer.

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The major components of a computer system are hardware and software. Hardware refers to the physical components of a computer, such as the motherboard, central processing unit (CPU), memory (RAM), hard drive, and others. These components work together to perform the basic functions of a computer. Software, on the other hand, refers to the programs and applications that run on a computer. This includes the operating system (such as Windows or macOS), as well as other applications like word processors, web browsers, and games. Firmware is a type of software that is stored on a hardware device, such as a computer's BIOS or a device's firmware. It provides low-level control for the hardware components and is typically not user-accessible or modifiable. In summary, a computer system is made up of both hardware and software components, with firmware serving as a type of software that is closely tied to the computer's hardware.

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(a)(i) What is booting?

Booting is the process of starting up a computer, during which the operating system is loaded from secondary storage into main memory (RAM) so that the computer becomes ready for use. It begins when power is switched on and the system runs its start-up instructions.

(a)(ii) Two differences between the types of booting (cold vs warm booting):

(Any two differences are acceptable.)

(b) What is a peripheral?

A peripheral is any device that is connected to and works with the computer but is not part of the central processing unit. Peripherals are used to put data into the computer, get results out, or store data (for example keyboard, printer, monitor and external disk).

(c) One example each:

• (i) Input device: keyboard (also mouse, scanner).
• (ii) Output device: monitor (also printer, speaker).
• (iii) Storage device: flash drive (also hard disk, CD/DVD).
• (iv) A component found inside the system unit: the motherboard (also CPU, RAM, power supply).

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(a) What is a register?

A register is a small, very high-speed temporary storage location built inside the Central Processing Unit (CPU). It holds a single piece of data, an instruction or an address that the processor is currently working on, so that it can be accessed almost instantly during processing.

(b) Two types of register:

• Accumulator (ACC)
• Program Counter (PC)

Other acceptable examples: Memory Address Register (MAR), Memory Data/Buffer Register (MDR/MBR), Instruction Register (IR), Index Register.

(c) Three functions of registers:

1. They temporarily hold data and instructions that are being processed by the CPU.
2. They store the memory address of the next instruction or of the data to be fetched (for example the Program Counter and Memory Address Register).
3. They hold the intermediate and final results of arithmetic and logic operations (for example the Accumulator).

(d) Three differences between a register and main memory:

(Any three of the above differences are acceptable.)

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(a) Definitions

(i) An array: An array is a data structure that holds a fixed number of data items of the same data type under a single variable name, with each item (element) identified by an index or subscript. For example, one array can store many students' scores, referred to as SCORE(1), SCORE(2), and so on.

(ii) A syntax error: A syntax error is a programming error that occurs when a statement breaks the grammatical rules of the programming language (for example a misspelt keyword, a missing bracket or a wrong statement structure). Such errors are detected by the translator (compiler or interpreter) and prevent the program from running until corrected.

(b) QBASIC program: multiples of three between 1 and 20 into a one-dimensional array

The multiples of three between 1 and 20 are 3, 6, 9, 12, 15 and 18 (six values).

REM Store multiples of 3 between 1 and 20 in an array
CLS
DIM M(6)
K = 0
FOR N = 1 TO 20
    IF N MOD 3 = 0 THEN
        K = K + 1
        M(K) = N
    END IF
NEXT N
PRINT "Multiples of three are:"
FOR I = 1 TO K
    PRINT M(I)
NEXT I
END

The loop tests each number from 1 to 20; when a number divides exactly by 3 (N MOD 3 = 0) it is stored in the next array position and later displayed.

(c) Convert \(D5FA_{16}\) to binary

Replace each hexadecimal digit with its 4-bit binary equivalent:

\[D = 1101,\quad 5 = 0101,\quad F = 1111,\quad A = 1010\]

\[\therefore D5FA_{16} = 1101\,0101\,1111\,1010_2 = 1101010111111010_2\]

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(a)(i) Define the term computer system.

A computer system is a complete set of interconnected components (hardware, software, data and people) that work together to accept data as input, process it under the control of stored instructions, and produce information as output, as well as store the data and results for future use.

(a)(ii) Major components of the computer system, with one example each:

• Hardware - the physical parts of the computer. Example: keyboard, monitor or CPU.
• Software - the programs and instructions that direct the hardware. Example: Microsoft Windows (operating system) or MS Word.
• Data/Information - the raw facts fed in and the processed results. Example: a list of students' scores.
• People (Users/Liveware) - the human beings who operate and use the system. Example: a computer operator or programmer.

(Where "components" is taken narrowly as hardware units: Input unit - keyboard; Central Processing Unit - microprocessor; Output unit - monitor; Storage unit - hard disk.)

(b)(i) Two activities involved in transferring data into information:

• Processing the data (for example sorting, calculating, classifying or summarising it).
• Organising and presenting the results in a meaningful, useful form (for example arranging into a report or table).

Other acceptable activities: collecting/inputting data, editing/validating, and storing.

(b)(ii) Acronyms in full:

• EDSAC - Electronic Delay Storage Automatic Calculator.
• EDVAC - Electronic Discrete Variable Automatic Computer.

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(a) A logic gate is an electronic circuit that receives one or more binary inputs, 0 or 1, and produces a single binary output according to a specified logical rule.

(b)

1. Standard logic gate: AND gate.
2. Alternative logic gate: NAND gate.

(c)(i) Logic symbol for an XOR gate

The XOR gate gives an output of 1 only when the two input values are different.

R = P ⊕ Q

(c)(ii) Truth table for the XOR logic gate

Inputs		Output
P	Q	R = P ⊕ Q
0	0	0
0	1	1
1	0	1
1	1	0

(d) Uses of logic gates:

1. They are used in arithmetic and logic units, such as binary adders in computers.
2. They are used in control and decision-making circuits, for example traffic-light controllers and burglar alarms.