Definition Of A Computer System PDF

Definition of a Computer System A computer system is a set of components designed to receive data (input), process it, and produce a meaningful result (output). It consists of: 1. Hardware: The physical, touchable components, like the keyboard, mouse, monitor, motherboard, and hard disk....

Definition of a Computer System A computer system is a set of components designed to receive data (input), process it, and produce a meaningful result (output). It consists of: 1. Hardware: The physical, touchable components, like the keyboard, mouse, monitor, motherboard, and hard disk. 2. Software: The intangible, logical components, including the operating system, applications, and data. 3. Human Component: The people involved in the design, management, and use of computer systems, including IT staff and users. The primary parts of a computer system are the CPU, memory, input/output devices, and storage devices, working together as a single unit to produce desired outputs. Examples include smartphones, tablets, PCs, servers, and supercomputers. The Five Generations of Computer Systems Each generation of computers brought key advancements in technology, size, cost, and functionality. First Generation (1940s - 1950s) Technology: Used vacuum tubes for circuitry and magnetic drums for memory. Programming: Programs were written in machine language and assembly language. Input was primarily through punch cards. Characteristics: Large, heavy, and consumed high amounts of power. Prone to overheating and frequent failures, requiring specialized cooling. Example: ENIAC (1945), UNIVAC (1951). Second Generation (1950s - 1960s)  Technology: Transistors replaced vacuum tubes, making computers faster, smaller, and more energy-efficient. Programming: Programs were written in assembly language and high-level languages like COBOL and FORTRAN. Memory: Used magnetic core memory for faster data access. Characteristics: Reduced size, cost, and heat generation compared to first- generation computers. More reliable and required less power. Example: IBM 1401, UNIVAC II. Third Generation (1960s - 1970s) Technology: Integrated Circuits (ICs), which placed multiple transistors on a single silicon chip, replaced individual transistors. Programming: Supported high-level languages and introduced Operating Systems that allowed multitasking and time-sharing. Memory: Magnetic disk storage became more common, providing greater data storage capacity and faster access. Characteristics: Smaller, more powerful, and more reliable than previous generations. Significantly reduced cost. Example: IBM System/360, UNIVAC 9000. Fourth Generation (1970s - 1980s) Technology: Microprocessors integrated thousands of ICs on a single chip, creating the first microcomputers (personal computers). Programming: Supported advanced high-level languages and Graphical User Interfaces (GUIs). Memory: Introduced semiconductor memory (RAM and ROM), significantly increasing memory efficiency. Characteristics: Small, affordable, and accessible for businesses and individuals. Marked the rise of personal computing. Example: Apple II, IBM PC (1981). Fifth Generation (1980s - Present) Technology: Artificial Intelligence (AI), parallel processing, quantum computing research, and advanced microprocessors. Programming: Emphasizes AI technologies, machine learning, and natural language processing. Memory: High-speed, large-capacity storage, including solid-state drives (SSDs) and cloud storage. Characteristics: Compact, highly powerful, and able to perform complex tasks. Continuous advancements in AI, machine learning, voice recognition, and robotics. Designed for interconnectivity and networking. Example: Smartphones, Supercomputers like IBM Watson and Fujitsu’s Fugaku. Von Neumann Architecture: Essential Concepts The Von Neumann architecture, introduced by John von Neumann in 1945, is based on the stored-program concept, where instructions and data are stored together in one memory unit. This innovation allows computers to run various programs by simply loading them from memory, unlike early machines (e.g., ENIAC), which needed manual rewiring to change tasks. Core Components of Von Neumann Architecture: 1. Central Processing Unit (CPU): Executes instructions and performs calculations. 2. Memory Unit: Stores both data and program instructions in the same space, enabling easy access and flexibility. 3. Input/Output Devices: Facilitate data exchange between the computer and external devices (e.g., keyboard, monitor). 4. Buses: Communication pathways that transfer data and instructions between the CPU, memory, and I/O devices. This architecture is the foundation of most modern computers, enabling them to be general-purpose and versatile. The Central Processing Unit (CPU) is the main electronic circuit responsible for executing a computer program’s instructions and managing the overall system operations. Programs are sets of instructions written in programming languages (e.g., C#, Java) that need to be loaded into main memory (RAM) to be executed. The operating system translates these instructions into machine instructions that the CPU can interpret, performing specific tasks like addition, subtraction, or data loading. The set of machine instructions a CPU can handle is known as its instruction set and is unique to each processor. Key components within the CPU include: Arithmetic and Logic Unit (ALU): Executes arithmetic operations (e.g., add, subtract) and logical operations (e.g., and, or, not). Control Unit (CU): Manages the operations of the ALU, memory, and input/output devices, directing them based on program instructions. It interprets program instructions, controls data movement between main memory and registers, and commands the ALU to perform specific operations. Registers: Small storage units within the CPU that temporarily hold data needed to execute instructions. Modern CPUs may also include additional components, like cache memory and sometimes even a Graphics Processing Unit (GPU), which will be covered in further detail later. 3.1 Control Unit (UC) Program Counter (PC): Register that contains the address of the next instruction to execute. Instruction Register (IR): Register that holds the current instruction, with the operation code and involved data. Decoder: Extracts and analyzes the operation code from the current instruction and sends control signals for its execution. CPU Clock: Generates regular pulses that set the pace for executing instructions; its speed is measured in hertz (Hz). Sequencer: Executes machine instructions by creating basic micro-orders in each clock cycle. 3.1.2. Arithmetic and Logic Unit (ALU) ALU: Realiza operaciones lógicas, aritméticas y de desplazamiento de bits en los datos que recibe de la unidad de control. Accumulator (AC): Registro especial que almacena resultados intermedios de operaciones lógicas y aritméticas. Status Register: Registro que indica situaciones especiales como resultados negativos o desbordamiento. Floating Point Unit (FPU): Circuito especializado para realizar operaciones matemáticas con números en punto flotante (fracciones y números muy grandes o pequeños), utilizando el estándar IEEE 754 para precisión. 3.1.3. Registrs Registers: Small, high-speed memory cells inside the CPU that store temporary data and work faster than conventional memory. Their size is determined by how many bits they can handle (e.g., 8, 16, 32, 64 bits). Types of Registers: 1. User Accessible Registers: Can be accessed by the user to optimize resource usage. Some types include: a. Address Registers: Hold memory addresses where data or instructions are located. b. Data Registers: Hold data. c. Flag Registers: Indicate conditions such as positive, negative, or null results, and overflow. 2. Internal Registers: Used by the CPU for internal operations and not accessible by instructions. Some types include: a. Program Counter (PC): Holds the address of the next instruction to execute. b. Instruction Register (IR): Holds the current instruction being executed. c. Memory Address Register (MAR): Holds the memory address for reading or saving data. d. Memory Buffer Register (MBR): Holds data to be read from or written to memory. 3.2 Buses Buses: Electrical or optical lines that transmit data between components like the CPU and memory. They carry groups of bits to enable communication within the computer. Types of Buses: Data Bus: Transmits data between the CPU, main memory, and input/output devices. The speed is measured in megahertz (MHz) or gigahertz (GHz). The word size (number of bits transferred simultaneously) is typically 64 bits, allowing the transfer of 8 bytes per clock cycle. Address Bus: Carries memory addresses between the CPU and memory, enabling access to specific memory locations. The size of the address bus determines how much memory can be addressed. For example, a 32-bit address bus can address 4 GB of memory. Control Bus: Sends control signals to coordinate and manage all activities within the computer system. 3.2 Memory Unit Memory Unit: Composed mainly of RAM (Random Access Memory) and ROM (Read-Only Memory), with RAM used to store data and instructions for active programs, enabling quick CPU access. RAM: A volatile memory used for temporarily storing data and instructions. It allows random access to any location, meaning data can be read and written at any address without sequential order. RAM is faster than hard drives, which would otherwise be used for instruction storage. Memory Cells: RAM consists of cells that store one word of data each, with each cell having a unique memory address. The size of the word depends on the microprocessor (e.g., 8, 16, 32, or 64 bits). Memory addresses match the size of the address bus. Volatility of RAM: RAM is volatile, meaning it loses its data when the computer is turned off because it stores information in capacitors that require periodic recharging.  Memory Operations: Memory Address Register (MAR): Stores the address of the memory cell to be accessed. Memory Buffer Register (MBR) (also called Memory Data Register (MDR)): Holds data being read from or written to memory. Control Unit: Manages read and write operations. To read, the address is placed in the MAR, and the data is moved to the MBR. To write, the address is placed in the MAR, and data is stored in the MBR before the write operation is executed. 3.25 Input and output Unit (I/O Unit) I/O Unit: Facilitates the exchange of information between the computer and external devices (peripherals). Peripherals: Devices that connect to the computer to exchange data. They can be classified as: Input Peripherals: Devices that send data to the computer, such as a keyboard, mouse, webcam, microphone, or scanner. Output Peripherals: Devices that receive data from the computer and present it to the user, such as a monitor, printer, speakers, or headphones. Input/Output Peripherals: Devices that can both send and receive data, like a touch screen. Storage Peripherals: Devices responsible for storing data, such as hard drives, DVD drives, or USB sticks, which can be internal or external. Communication Peripherals: Devices that enable communication between computers or between a computer and an external device, such as network cards, Bluetooth cards, and port controllers. I/O Unit Function: The I/O unit serves as an interface between the CPU and peripherals, addressing issues like differences in transmission speed and data formats. It ensures that peripherals can communicate with the CPU effectively. I/O Modules: Composed of peripheral controllers (to manage communication with the CPU) and I/O ports (which allow peripherals to connect to the computer’s buses). CPU Features: Clock Speed: Measures how many cycles the CPU executes per second, typically in gigahertz (GHz). Instruction Set: The collection of machine instructions a CPU can process. Some CPUs have simpler instruction sets for elementary operations, while others can handle both elementary and complex operations, with complex operations being slower. Word, Data Bus, and Address Bus Size: The size of these components determines how much data or address information the CPU can handle at once. Memory Hierarchy: Memory in a computer system is organized in a hierarchy based on capacity, access speed, and cost per bit: 1. CPU Registers: Small, fast memory integrated into the CPU, used during instruction execution. They have low capacity but high speed. 2. Cache Memory: A fast memory that stores frequently accessed data and instructions, acting as a buffer between RAM and the CPU. It speeds up data access by avoiding slower RAM accesses. 3. Main Memory (RAM): Holds active program instructions and data. It has a larger capacity than cache but is slower. 4. Secondary Memory: Permanent storage for data and programs. It has a much larger capacity than main memory and is non-volatile, but slower. Examples include hard drives (HDD), solid-state drives (SSD), and optical media (CD/DVD).