TExES Computer Science 8-12 (241)

The central processing unit (CPU) serves as the brain of a computer system, executing instructions and performing calculations. Modern CPUs contain multiple cores, allowing parallel processing of tasks. The CPU operates through a fetch-decode-execute cycle, retrieving instructions from memory, interpreting them, and carrying out the specified operations.

Random Access Memory (RAM) provides temporary storage for data and programs currently in use. RAM is volatile, meaning its contents are lost when power is removed. The amount of RAM directly affects system performance, as insufficient memory forces the system to use slower storage devices for temporary data.

Read-Only Memory (ROM) contains permanent instructions that remain intact without power. ROM typically stores firmware and boot instructions necessary for starting the computer. Modern systems use variations like EEPROM (Electrically Erasable Programmable ROM) that allow limited rewriting.

Storage devices provide persistent data retention. Hard Disk Drives (HDDs) use magnetic platters and read/write heads to store data. Solid State Drives (SSDs) use flash memory with no moving parts, offering faster access times and greater durability. Storage capacity is measured in bytes, with modern devices reaching terabyte (TB) capacities.

The motherboard serves as the main circuit board connecting all components. It contains the chipset that manages data flow between the CPU, memory, and peripherals. Expansion slots allow adding graphics cards, network adapters, and other components.

Input devices include keyboards, mice, touchscreens, scanners, microphones, and cameras. Output devices include monitors, printers, speakers, and projectors. Peripheral devices connect through various interfaces including USB, HDMI, DisplayPort, and Thunderbolt.

System software manages hardware resources and provides a platform for running applications. The operating system (OS) handles process management, memory allocation, file systems, and user interfaces. Common operating systems include Windows, macOS, Linux, iOS, and Android.

Application software performs specific user tasks. Productivity software includes word processors, spreadsheets, and presentation programs. Creative software encompasses image editors, video editors, and audio production tools. Communication software includes email clients, messaging applications, and video conferencing tools.

Utility software maintains and optimizes system performance. Antivirus programs detect and remove malware. Disk utilities manage storage, including defragmentation and partition management. Backup software creates copies of important data for recovery purposes.

Development software supports creating other software. Integrated Development Environments (IDEs) combine code editors, compilers, debuggers, and other tools. Version control systems track changes to source code over time. Testing frameworks automate software verification.

Networks connect computers to share resources and communicate. Local Area Networks (LANs) cover limited geographic areas like buildings or campuses. Wide Area Networks (WANs) span larger distances, connecting multiple LANs. The Internet is a global WAN connecting billions of devices.

Network topologies describe physical or logical arrangements of connected devices. Bus topology connects all devices to a single cable. Star topology connects devices to a central hub or switch. Ring topology forms a circular connection pattern. Mesh topology provides multiple paths between devices for redundancy.

The OSI (Open Systems Interconnection) model divides network communication into seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. Each layer performs specific functions and communicates with adjacent layers.

The TCP/IP model provides a practical framework for Internet communication. The Network Access layer handles physical transmission. The Internet layer manages logical addressing and routing using IP addresses. The Transport layer ensures reliable data delivery using TCP or faster but unreliable delivery using UDP. The Application layer supports user-facing protocols like HTTP, FTP, and SMTP.

IP addresses uniquely identify devices on networks. IPv4 uses 32-bit addresses written as four decimal numbers separated by dots (e.g., 192.168.1.1). IPv6 uses 128-bit addresses written in hexadecimal to accommodate growing Internet needs.

Domain Name System (DNS) translates human-readable domain names to IP addresses. When users enter a URL, DNS servers resolve the domain to the appropriate IP address, enabling connection to the desired server.

Routers direct traffic between networks, determining optimal paths for data packets. Switches connect devices within a network, forwarding frames based on MAC addresses. Firewalls filter traffic based on security rules, protecting networks from unauthorized access.

Cloud computing delivers computing services over the Internet. Infrastructure as a Service (IaaS) provides virtualized computing resources like servers and storage. Platform as a Service (PaaS) offers development and deployment environments. Software as a Service (SaaS) delivers complete applications accessible through web browsers.

Public clouds share resources among multiple organizations. Private clouds dedicate resources to single organizations for greater control and security. Hybrid clouds combine public and private elements, allowing organizations to balance cost and security requirements.

Cloud benefits include scalability, allowing resources to expand or contract based on demand. Pay-per-use pricing eliminates large upfront investments. Geographic distribution improves performance and reliability. Automatic updates reduce maintenance burden.

Computers use binary (base-2) numbering with only two digits: 0 and 1. Each binary digit is called a bit. Eight bits form a byte, capable of representing 256 different values.

Converting decimal to binary involves repeated division by 2, recording remainders. For example, decimal 13 converts to binary 1101: 13÷2=6 remainder 1, 6÷2=3 remainder 0, 3÷2=1 remainder 1, 1÷2=0 remainder 1.

Hexadecimal (base-16) provides compact representation of binary data. Hex digits 0-9 and A-F represent values 0-15. Each hex digit equals four binary bits. For example, hex FF equals binary 11111111 equals decimal 255.

ASCII (American Standard Code for Information Interchange) encodes text characters as numbers. Standard ASCII uses 7 bits for 128 characters including letters, digits, and symbols. Extended ASCII uses 8 bits for 256 characters.

Unicode provides universal character encoding supporting virtually all written languages. UTF-8 encoding uses variable-length sequences of 1-4 bytes, maintaining compatibility with ASCII while supporting over a million characters.

Images use pixels (picture elements) arranged in grids. Bitmap images store color values for each pixel. Color depth determines available colors: 8-bit allows 256 colors, 24-bit allows over 16 million colors. Resolution measures image dimensions in pixels.

Audio digitization samples sound waves at regular intervals. Sample rate (measured in Hz) determines frequency accuracy. Bit depth determines amplitude precision. Higher values produce better quality but larger files.