WAEC Computer Science 2017
Questions & Answers

The Arithmetic Logic Unit (ALU) is a core component of the Central Processing Unit (CPU) that performs both basic arithmetic operations (such as addition, subtraction, multiplication, and division) and logical operations (such as comparisons, AND, OR, and NOT). It processes data based on instructions from the control unit but does not handle storage, input, or output functions directly.

Third-generation computers (roughly 1964-1971) were characterized by the use of integrated circuits (ICs), which combined multiple transistors on a single chip, leading to smaller size, higher speed, lower cost, and increased reliability compared to previous generations. Vacuum tubes were first-generation, magnetic drums were early storage in second-generation, and microprocessors defined fourth-generation.

A compiler is a program that translates source code written in a high-level programming language (e.g., C++, Java) into machine code or object code that the computer's processor can execute directly. This process involves syntax checking, optimization, and generation of executable code, unlike interpreters which execute line-by-line.

A scanner is an input device that optically captures images, printed text, or graphics from physical documents and converts them into digital format for storage or editing in a computer. Plotters output vector graphics, while joysticks and trackballs are pointing devices for navigation.

The decimal number 255 in binary is calculated as 2^8 - 1 = 256 - 1 = 11111111 (eight 1s), representing the maximum value for an 8-bit unsigned integer. Each bit position corresponds to powers of 2: 128+64+32+16+8+4+2+1=255.

The operating system (OS) is system software that acts as an intermediary between users and hardware, managing resources like CPU time, memory allocation, device drivers, and file systems to ensure efficient and secure operation of the computer.

In a star topology, all devices (nodes) are connected to a central hub or switch, which manages data transmission and allows easy addition/removal of devices. Failure of the central hub affects the entire network, unlike bus (linear) or ring (circular) topologies.

Read-Only Memory (ROM) is non-volatile memory that retains data even when powered off, typically used to store firmware or BIOS instructions that are essential for booting and basic system operations and cannot be easily modified by the user.

Utility software consists of programs that perform maintenance or support tasks, such as antivirus software which scans for and removes malicious threats to protect the system. Word processors, spreadsheets, and databases are application software for productivity.

A byte is the fundamental unit of digital information storage, consisting of 8 bits, capable of representing 256 different values (0-255). A nibble is 4 bits, a word is typically 16 or 32 bits, and a kilobyte is 1024 bytes.

Flash memory is non-volatile semiconductor storage that retains data without power, commonly used in USB drives and SSDs. RAM and cache are volatile (lose data on power off), and virtual memory uses disk space as temporary RAM.

Database Management Systems (DBMS) like MySQL or Access are designed to store, retrieve, update, and manage large volumes of structured data efficiently, ensuring data integrity, security, and relational querying via SQL.

File Transfer Protocol (FTP) is a standard network protocol for transferring files between a client and server over TCP/IP networks, supporting upload, download, and directory management. SMTP is for email sending, HTTP for web pages, and POP3 for email retrieval.

Ctrl + Z is the universal keyboard shortcut in most software applications (e.g., Microsoft Office, Adobe) to reverse or undo the most recent action, allowing users to correct mistakes quickly without menu navigation.

Binary 1101 converts to decimal by positional values: 1*2^3 (8) + 1*2^2 (4) + 0*2^1 (0) + 1*2^0 (1) = 8 + 4 + 0 + 1 = 13. This is the standard base-2 to base-10 conversion method.

A router is a networking device that forwards data packets between computer networks, such as connecting a local area network (LAN) to the internet (WAN), using IP addresses and routing tables for efficient path selection.

Primary storage, or main memory like RAM, provides fast, temporary storage directly accessible by the CPU for active data and programs during execution. HDD, SSD, and optical discs are secondary storage for long-term data retention.

BIOS (Basic Input/Output System) is firmware stored on the motherboard's ROM that initializes hardware during boot-up, performs POST (Power-On Self-Test), and provides runtime services for OS and applications to interact with hardware.

A primary key is a unique identifier for each record in a database table, ensuring no duplicates and enabling efficient data retrieval and relationships. Foreign keys link tables, composite keys combine multiple columns, and candidate keys are potential primaries.

FORTRAN (Formula Translation) is one of the earliest high-level languages, designed for scientific and engineering computations, using English-like syntax that's human-readable and independent of machine architecture, unlike low-level machine or assembly code.

Data transfer rate measures the speed of data movement over a network or storage medium, typically in bits per second (bps) or bytes per second (Bps), where 1 byte = 8 bits. Hz measures frequency, PPI/DPI are for resolution.

A computer worm is a standalone malware that replicates itself to spread across networks without needing a host file, often exploiting vulnerabilities to consume bandwidth or deliver payloads, differing from viruses which attach to files.

System software, like the Linux kernel, manages hardware and provides a platform for application software to run, handling tasks such as process management, memory allocation, and device control. Excel and Illustrator are applications, browsers are utilities.

Decimal 8 in binary is 1000, as 1*2^3 (8) + 0*2^2 (0) + 0*2^1 (0) + 0*2^0 (0) = 8. This is determined by repeated division by 2 and recording remainders from last to first.

A Wide Area Network (WAN) spans large geographic areas, connecting multiple LANs via technologies like leased lines or satellites, enabling global communication such as the internet, unlike smaller-scale networks.

A network hub is a basic device that connects multiple Ethernet devices, making them act as a single network segment by broadcasting incoming data to all ports, though less efficient than switches due to potential collisions.

The .zip extension denotes files archived and compressed using ZIP format, reducing file size for efficient storage and transfer, supporting multiple files in one container. PDF is for documents, MP3 for audio, HTML for web pages.

Disk formatting initializes the storage medium by creating a file system (e.g., NTFS, FAT32) structure for organizing files, marking sectors, and allocating space, often erasing existing data in the process.

The <table> tag in HTML defines a table structure, containing elements like <tr> for rows, <td> for cells, and <th> for headers, enabling tabular data display on web pages. <div> is for divisions, no <list>, <form> for inputs.

Electrically Erasable Programmable Read-Only Memory (EEPROM) is non-volatile, allowing data retention without power and electrical erasure/reprogramming at byte level, used in BIOS and flash storage. RAM, DRAM, SRAM are volatile.

Resolution in graphics is the detail level measured by total pixels (e.g., 1920x1080), determining image clarity; higher resolution means more pixels for sharper images, independent of color depth or file attributes.

Fifth-generation computers (1980s-present) emphasize artificial intelligence, parallel processing, and natural language processing using advanced technologies like ULSI chips, aiming for human-like interaction via voice recognition and expert systems.

The DIR command in DOS (Disk Operating System) lists files and subdirectories in the current or specified directory, showing names, sizes, dates, and attributes for file management.

Decryption reverses the encryption process using a key to convert ciphertext back to readable plaintext, ensuring secure data access. Encryption scrambles data, compression reduces size, hashing creates fixed-size digests.

A table in a relational database is a structured collection of related records (rows) and fields (columns) representing entities, forming the basic unit for data storage and manipulation.

A USB flash drive is a portable secondary storage device using flash memory to store data persistently, offering high capacity and plug-and-play connectivity. Mouse, monitor, and speaker are input/output peripherals.

John Mauchly, along with J. Presper Eckert, designed and built ENIAC (1945), recognized as the first practical general-purpose electronic digital computer, used for complex calculations like artillery trajectories during WWII.

A byte is standardized as 8 bits, allowing representation of 256 unique combinations (2^8), serving as the basic addressable unit in most computing systems for characters and small data values.

Microsoft Outlook is an email client and personal information manager that handles sending/receiving emails, calendars, contacts, and tasks, integrating with Exchange servers for enterprise use.

A loop in programming (e.g., for, while) repeatedly executes a code block based on a condition, automating repetitive tasks like iterating over arrays or processing data until a criterion is met, improving efficiency.