Computer programming 1 Ultimate Study Guide

Computer Networking Fundamentals

• Network Definition: A collection of computers connected by communication devices that enable message transmission and data communication.
• Network Topology: The structural arrangement of elements, nodes, and links within a computer network.

Network Topologies

• Point-to-Point: The simplest configuration, establishing a permanent direct link between two endpoints; requires a cross-cable connection to link two computers directly.
• Bus: Employs a single central backbone cable to which every host, computer, or server connects.
• Star: Features individual point-to-point connections from every host or peripheral to a central device such as a hub or switch.
• Ring: Devices are arranged in a closed circular loop where data travels unidirectionally; each device houses a receiver and transmitter, functioning as a repeater to maintain signal integrity.
• Mesh: Network value scales proportionally to the exponent of the number of subscriber endpoints; fully interconnected among communicating groups.
• Tree: A hierarchical structure headed by a single root node connected to lower-level nodes via point-to-point links, which in turn connect down to subsequent levels.

Core Networking Terms & Protocols

• SSID (Service Set Identifier): Identifies and displays wireless local networks.
• NIC (Network Interface Controller): Hardware card or adapter linking a computer to a physical or wireless network segment.
• DHCP (Dynamic Host Configuration Protocol): Automated protocol providing plug-and-play IP address assignment to network clients without manual administration.
• ARP (Address Resolution Protocol): Resolves network layer addresses into physical link layer addresses.
• Router: Connects two or more distinct network lines, directing data packets across an overlay internetwork.
• Network Switch: An intelligent distribution device forwarding packets solely to destination ports rather than broadcasting to all ports.
• Subnetwork (Subnet): A logical subdivision of an IP network created via subnetting.
• MAC Address: A unique hardware identifier permanently embedded into a NIC's read-only memory or firmware by its manufacturer.
• High-Level Protocols:
  • FTP (File Transfer Protocol): Facilitates file exchanges across TCP-based networks.
  • DNS (Domain Name System): Hierarchical naming system translating human-readable names to network resources.
  • HTTP (Hypertext Transfer Protocol): Application protocol underpinning distributed hypermedia systems.
  • SMTP (Simple Mail Transfer Protocol): Standard for email transmission across IP networks.

IP Addressing Classes

• Class A: Spans $0.0.0.0$ to $126.255.255.255$; contains $126$ networks and $16{,}777{,}214$ possible host addresses; targeted at massive multinational organizations.
• Loopback: The reserved $127.0.0.0$ network utilized for internal software testing and hardware debugging.
• Class B: Spans $128.0.0.0$ to $191.255.255.255$; contains $16{,}384$ networks and $65{,}534$ addresses per network; targeted at Internet Service Providers, major hospitals, and colleges.
• Class C: Spans $192.0.0.0$ to $223.255.255.255$; contains $2{,}097{,}152$ networks with $255$ endpoints each; allocated to small and mid-sized businesses.
• Class D: Spans $224.0.0.0$ to $239.255.255.255$; strictly dedicated to multicast transmissions.
• Class E: Spans $240.0.0.0$ to $255.255.255.255$; reserved for experimental implementation.

OSI Reference Model

• Framework: Open System Interconnection (OSI) is a 7-layer theoretical conceptual model representing communication protocols without executing functions directly.
• Layer 1 – Physical: Handles bit streams over electrical, optical, or radio channels (e.g., Fast Ethernet, RS232, ATM).
• Layer 2 – Data Link: Encodes and decodes packets into frames and bits; handles flow control and frame synchronization; split into Media Access Control (MAC) and Logical Link Control (LLC) sublayers.
• Layer 3 – Network: Manages routing, virtual circuits, switching, addressing, and packet sequencing.
• Layer 4 – Transport: Ensures transparent, complete end-to-end data transfer, flow management, and error correction between host applications.
• Layer 5 – Session: Coordinates, creates, regulates, and terminates conversational dialogues between applications.
• Layer 6 – Presentation (Syntax Layer): Translates, standardizes, and encrypts payload representations between network and application syntax.
• Layer 7 – Application: Interfaces directly with user applications; delivers software services like file handling and email (e.g., Telnet, FTP).

The Internet & Switching Mechanisms

• Development History:
  • USSR launched Sputnik on October 4, 1957, driving the shift from sequential Batch Processing to concurrent Time-Sharing.
  • US President Eisenhower authorized DARPA (later separated into NASA and ARPANET).
  • Motivated by Cuban missile reconnaissance in 1962, ARPANET designed a decentralized, survivable network where the loss of one server does not sever connectivity.
  • ARPANET created the Data Exchange Network in 1969 connecting four initial university nodes: University of California in Los Angeles, Stanford University, University of California in Santa Barbara, and University of Utah.
  • Ray Tomlinson introduced email in 1972 after sending the first email in 1971.
• Network Scopes:
  • Intranet: Internal, strictly authenticated corporate network.
  • Extranet: Controlled private segment providing designated external vendors, partners, or consumers access to intranet partitions.
• IP Versions: IPv4 is a widely used connectionless, packet-switched standard; IPv6 serves as the next-generation replacement protocol.
• Circuit Switching vs. Packet Switching:
  • Circuit Switching: Primarily utilized in legacy telephone networks; reserves a dedicated physical end-to-end circuit via signaling protocols; exclusive channel occupation without intermediate routing headers.
  • Packet Switching: Utilized in computer networks; segments data into packets bearing header routing metadata; processed via store-and-forward mechanisms across intermediate routers and switches without dedicated circuit reservation.
  • Sub-types: Virtual Circuit (VC, primarily Data Link Layer) and Datagram (used at Data Link and Network Layers).

Computer Security & Cryptography

• Core Objective: Protecting computer hardware, systems, and digital assets from unauthorized use, disruption, destruction, and theft.
• Five Primary Threats: Theft of data, vandalism (viruses), fraud, invasion of privacy, and copyright infringement/piracy.
• Handshaking Protocol: Automated preliminary negotiation between two devices (e.g., dial-up modem tones or PC-to-printer setup) defining transfer speed, coding alphabets, parity, and access credentials.
• Cryptography Fundamentals:
  • Encryption (Encipherment): Algorithmic transformation of plaintext into ciphertext.
  • Decryption (Decipherment): Restoring ciphertext back to clear text using an authorized key.
  • Enigma Machine: Historic electro-mechanical rotor cipher created by Arthur Scherbius post-WWI, utilized by Nazi Germany during WWII.
  • Symmetric Encryption: Uses an identical shared secret key for both ciphering and deciphering.
  • Asymmetric Encryption: Employs a mathematically paired public key (widely distributed for encryption) and private key (kept secret by recipient for decryption).

Legal Frameworks & Cyber Legislation

• Republic Act 8792 (E-Commerce Act of 2000): Signed on June 14, 2000; took effect on June 19, 2000. Formally validates electronic data messages, electronic documents, digital signatures, and electronic contracts; establishes finality for ATM network banking transactions.
• Republic Act No. 10173 (Data Privacy Act of 2012): Governs processing of private, personal, and identifiable information; mandates penalties up to 6 years imprisonment and fines up to PHP 5,000,000 for non-compliance.
• Cybercrime Prevention Act of 2012: Penalizes offences including illegal access, child pornography, identity theft, cybersex, cybersquatting, and libel; introduces a catch-all clause applying Revised Penal Code penalties at higher severities to computer-facilitated crimes.

Questions & Discussion

• Question: The simplest topology creates a link in a network between two endpoints.
  • Answer: Point-to-point. A cross-cable connection is needed to connect two computers directly.
• Question: Which of the following terms provides automatic IP to computers in a network?
  • Answer: Dynamic Host Configuration Protocol (DHCP). This provides a plug-and-play function in modern routers.
• Question: Which of the following classes of IP is used for common mid-sized companies?
  • Answer: Class C. Each network consists of $255$ individual IP addresses or endpoints.
• Question: What was the name of the Russian space satellite that was launched on 1957 and was considered as the start of the internet?
  • Answer: Sputnik. It orbited the Earth, initiating the American project to reach the Moon and ultimately catalyzing the development of the Internet.
• Question: What are the advantages of using the Internet?
  • Answer: Communication, information, learning, entertainment, social networks, and e-commerce.
• Question: What is the meaning of ARPANET?
  • Answer: Advanced Research Projects Agency Network, an agency that separated from DARPA to develop interconnected computer networks.
• Question: What is computer security?
  • Answer: The protection of computer systems and information from harm, theft, and unauthorized use.
• Question: Identify the threats that computer security is trying to prevent from happening.
  • Answer: Theft of data, vandalism, fraud, invasion of privacy, and copyright infringement or piracy.
• Question: What is the Republic Act No. 10173 or the Data Privacy Act of 2012?
  • Answer: A law focused on protecting personal, private, and sensitive information from unauthorized processing.