Introduction to Computer Architecture

• Computer architecture includes the design of a computer system, its components, and their organization, covering both hardware and software.
• Computer architecture influences computing systems' capabilities and limitations, affecting execution speed and application effectiveness.

History of Computing

• Information technology (IT) involves using computers to store, retrieve, transmit, and manipulate data or information.
• A computer is an electronic device controlled by instructions in its memory, accepting data (input), processing it, producing information (output), and storing it for future use.

Computer Hardware vs. Software

• Computer hardware includes electronic devices, input/output, memory/storage, and networking/communication devices.
• Computer software includes system software, operating systems, device drivers, and application software.

Von Neumann Architecture

• The von Neumann architecture, proposed in 1945, is the template for modern computers.
• The architecture includes a processing unit (ALU and registers), a control unit, memory for data and instructions, external mass storage, and input/output mechanisms.

Computer Hardware Components

Motherboard

• A motherboard is a computer's primary printed circuit board (PCB) that connects hardware components like the CPU, memory, and storage devices.
• It provides electrical connections and pathways for data transfer between components and includes interfaces for external connections.

Central Processing Unit (CPU)

• A central processing unit (CPU) performs decision-making, arithmetic, and data manipulation by executing billions of instructions per second.
• The CPU's operation is controlled by a program listing what to do.
• CPU speed is measured in gigahertz (GHz), indicating clock frequency or rate.
• A processor has three main components: a control unit, an arithmetic logic unit (ALU), and registers.
• The control unit directs operations, the ALU performs calculations, and registers provide temporary storage.
• A machine cycle has four basic steps: fetching data and instructions, decoding instructions and sending them to the ALU, performing calculations in the ALU, and storing results.

Memory

• Memory encompasses various types of storage for temporarily or permanently holding data and instructions for processing.
• Key types include RAM, ROM, cache memory, HDDs, and SSDs.
• Memory impacts system performance and multitasking.
• Memory can be either volatile, needing power to retain memory, such as RAM, or non-volatile, holding contents without power, such as ROM and flash memory.
• RAM is fast, non-persistent and is used for processing, whereas ROM is persistent and is used to start up the computer.
• Static RAM (SRAM) is expensive with low power, and Dynamic RAM (DRAM) is cheaper with higher power.
• Flash memory acts like both RAM and ROM, allowing information writing and retaining data when powered off.

Memory Addresses

• Memory addresses are numerical identifiers that specify locations within the computer's memory.
• Each byte of memory has a unique address, allowing the CPU to access and manipulate stored data efficiently.

Logical Addresses

• Logical addresses are generated by the CPU during program execution and serve as references to access physical memory.
• Logical addresses are virtual and mapped to physical addresses using a memory management unit and a page table.

Physical Addresses

• Physical addresses represent the physical location of data in memory accessible by the CPU through logical addresses.
• The term physical address space refers to all physical addresses corresponding to logical addresses.

Peripherals

Internal Adaptation

• Internal adaptation involves using adapter cards and ports to connect and interact with different components and peripherals.
• Adapter cards extend functionality beyond built-in capabilities, while ports facilitate connections to external devices.

Adapter Cards

• An adapter card is an internal expansion card that enables communication with peripherals, such as video and sound cards.
• A video card generates output images for a display device and a sound card provides input and output of audio signals.

Ports

• A port is a physical or virtual interface enabling communication with external peripherals or networks through specific connections, protocols, and data transfer rates.

Speed Comparisons

• CPU registers have a latency of 1–3 nanoseconds and a capacity of less than 1 KB.
• CPU caches have a latency of 2–12 nanoseconds and a capacity of 1–8 MB.
• Main memory (RAM) has a latency of 10–60 nanoseconds and a capacity of 1 GB to 128 GB.
• SSD using PCIe has a latency of ~25,000 nanoseconds and a capacity of 64 GB to 2 TB.
• SSD using SATA has a latency of ~50,000 nanoseconds and a capacity of 64 GB to 2 TB.
• Hard drive using SATA has a latency of ~1,000,000 to 10,000,000 nanoseconds and a capacity of 128 GB to 10 TB.

External Peripherals

• External peripherals enhance functionality include input devices, output devices, storage devices, and networking devices.
• Common examples of external peripherals are monitors, mice, and keyboards.

Topic 2: Computer Algorithms

• Computer algorithms process input data through mathematical operations or logical operations, accessing memory, controlling hardware, and producing output results.
• An algorithm is a finite set of precise instructions for performing a computation or solving a problem.
• A program is a type of algorithm, but not all algorithms are programs.
• Algorithms typically have input, output, definiteness, correctness, finiteness, effectiveness, and generality.
• Pseudocode is a high-level, informal programming language used to express algorithms clearly without specific syntax constraints.

Searching Algorithms

• A searching algorithm finds a specific item within a data collection, and examples include linear search, binary search, hashing, DFS, BFS, and interpolation search.

Linear Search

• A linear search algorithm checks each element sequentially until it finds the target value.
• If target value matches an element in the collection, its index (or position) is returned.

Sorting Algorithms

• A sorting algorithm arranges elements in a specific order within a list or array.

Bubble Sort

• Bubble sort algorithm takes successive elements and 'bubbles' them up the list.
• It is among the simplest sorting algorithms.

Topic 3: Binary Representation

• Data representation on computers involves encoding, storing, and manipulating information.
• Binary representation uses bits (0 and 1) grouped into bytes (8 bits).
• Computers use binary, decimal, octal, and hexadecimal systems for numbers.
• Character encoding schemes like ASCII and Unicode map characters to numeric codes.
• Computers handle non-textual data such as images, audio, and video using formats like JPEG or MP3.
• Data structures like arrays and linked lists organize data in memory.

Logic Gates

• Logic gates are fundamental components of digital circuits that perform basic logical operations on binary inputs to produce binary outputs.
• Types of logic gates include AND, OR, NOT, NAND, NOR, and XOR gates.
• Complex logical functions can be implemented by connecting logic gates.

Transistors

• Transistors are semiconductor devices that control current flow based on applied voltage, arranged to create basic operations in logic gates.
• PMOS transistors switch on with low voltage, and NMOS transistors switch on with high voltage.

Truth Tables

• A truth table is a tabular representation showing the outputs of a logical expression or a combination of inputs.
• Truth tables define the behavior of logic gates, expressions, and Boolean functions, providing clarity and systematic analysis.

Logic Gates

AND Gate

• An AND gate produces a true output (1) only when all inputs are true.

NOT Gate

• A NOT gate inverts the input signal; a logic high (1) becomes a logic low (0), and vice versa.

OR Gate

• An OR gate produces a true output (1) when at least one input is true; otherwise, the output is false (0).

NAND Gates

• NAND gate outputs a low voltage (0) if — and only if — both inputs are high voltage (1).

XOR Gate

• An XOR gate produces a true output (1) if the number of true inputs is odd - the output is true (1) if the inputs are different (one true, one false).

Adders

• An adder is a digital circuit used to perform addition of binary numbers.

Half Adder

• A half adder adds two single binary digits, producing a sum bit and a carry bit.

Full Adder

• A full adder adds three binary digits, producing a sum bit and a carry bit.

Representing Data

Data Types

• Common data types include integers (int), characters (char), strings, floating-point numbers (float), and double-precision floating-point numbers (double).

Number Representation

• Computers use the binary system (base 2) to represent data with 0s and 1s.
• The hexadecimal number system (base 16) simplifies binary representation.

Text Representation

• Text is represented in binary using standards like ASCII and Unicode.
• ASCII uses 1 byte per character, while Unicode uses UTF-16 (2 bytes) or UTF-8 (variable bytes).

Image Representation

• Images are displayed using pixels with three colors: red, green, and blue (sub-pixels).
• Typically, 3 bytes per pixel are assigned, written in hex.

Topic 4: Data Storage

• Data is stored in various file types, each identified by a file extension.
• File type markers (magic numbers) are sequences of bytes at the beginning of a file that uniquely identify its format.
• File compression reduces file size using algorithms and techniques.

File Compression

• Lossless compression compresses files into smaller sizes without data loss, allowing them to be decompressed back to the original.
• Lossy compression removes data in a way that cannot be reversed, such as in JPEG images and MP3 audio.
• File compressibility depends on the algorithm, data patterns, and whether the file is already compressed.

Topic 1: Databases

• A database is a structured data collection allowing access, retrieval, modification, and usage.
• A database management system (DBMS) is software for creating and managing databases, acting as an interface between users and the database.
• DBMS functionalities: data storage, transaction support, recovery, authorization, remote access, and constraint enforcement.
• Main database types: relational (RDB), object-oriented (OODB), network, and non-relational (NoSQL).

Relational Databases

• Relational databases organize data into tables with rows and columns, allowing efficient querying and manipulation using SQL.

Entity–Relationship Diagrams (ERDs)

• An entity-relationship diagram (ERD) models the problem with symbols visualizing entities and their interrelationships.
• Entities are drawn as rectangles, relations as diamonds, and attributes as ovals.
• Relations can be one-to-many (1:M), many-to-many, or one-to-one.
• It's useful to add a quantity attribute in the relationship between order and product; to reduce redundancies.

Adding Attributes

• Attributes are information about the entity, drawn as ovals.
• Unique attributes become primary keys, which are unique data identifiers.
• Surrogate key is a number used as a primary key.

Adding Attributes to Relationships

• Determine the attributes by asking what information you need about the customer, order, product, and brand.

Topic 2: Convert an ERD to Tables

• Convert the ERD to tables to create the database.
• Entities become tables with their attributes as columns.

Foreign Keys

• A foreign key is an attribute in a database table that links to another table, representing a relationship between them through shared data
• One-to-many relations have a foreign key in the "many" entity, referencing the primary key of the "one" entity.
• Many-to-many relations require a junction table with primary keys of both related tables, acting as both foreign and primary keys.
• Primary key with multiple columns is called a composite primary key.
• One-to-one relations are possible and can be used for access control (confidential data) and table inheritance.

Topic 3: Create Tables Using SQL

• Use Structured Query Language (SQL) to create tables within the database.

CREATE TABLE Syntax

• The CREATE TABLE statement creates a new table by defining its structure, including column names, data types, constraints, and indexes.

INSERT INTO Syntax

• The INSERT INTO command adds data to the created table.

Extract Data

• We use SQL commands to extract data from the database.

SELECT Command

• SELECT is the primary command that is used in SQL to retrieve data. Often with the WHERE keyword, to only show data if the expression is true

LIKE Operator

• The LIKE operator checks if text matches a particular pattern.

IN Operator

• The IN operator checks if a value is in a list of possible values.

ORDER BY

• The ORDER BY keyword displays results in a particular order that can be either ascending, or descending.

AS (alias)

• The AS keyword renames a column.

LIMIT and OFFSET

• The LIMIT clause restricts the number of rows a select statement returns.
• The OFFSET clause skips the offset rows before returning data from the rows.

Aggregate Data

• Aggregate functions work over multiple rows and combine them, including count(), sum(), avg(), min(), and max().

HAVING Clause

• The HAVING clause occurs after the aggregates have finished, similar to WHERE.

VIEW

• View is a saved query that works like a regular table, except the rows are not able to be edited; it’s useful if there is a large and complex query.

View

• A view is a saved query, with the rows not able to be edited.

Topic 4: Extracting Data From Multiple Tables

Combining Tables

• Tables are often needing to be combined using a JOIN to connect the tables that contain primary and foreign keys. Also referred to as an ON Clause

ON Clause

• ON clauses connect the primary and foreign keys

USING Clause

• USING clause replaces ON clause, which only can work if the column is in two tables