*Memory Management
Memory management involves the management of a computer's primary memory (RAM) to optimize its usage and ensure efficient allocation of memory resources.
Memory Hierarchy: Memory hierarchy consists of different levels of memory, each offering varying capacities, access speeds, and costs. The memory hierarchy usually includes the following levels:
Registers: Fastest and smallest storage locations directly accessible by the CPU. They store frequently accessed data and instructions.
Cache: Small, high-speed memory that stores a subset of data from the main memory. It helps reduce the average time taken to access memory by exploiting the principle of locality. There are 3 levels of cache, L3(stores in MB), L2(stores in KB,MB), and L1(stores in KB)
Main Memory (RAM): Provides temporary storage for data and instructions during program execution. It is larger in size but slower than cache.
Secondary Storage: Includes hard disk drives (HDDs), solid-state drives (SSDs), and other non-volatile storage devices. It offers larger capacities but slower access speeds compared to main memory.
{This is the basic tradeoff, higher the storage lower is this accessing speed.}
Memory Allocation: Memory allocation refers to the process of assigning memory segments to programs or processes. It involves the following key techniques:
Fixed Partitioning: Memory is divided into fixed-size partitions, and each partition can accommodate one process. It is inflexible and leads to external fragmentation.
Dynamic Partitioning: Memory is divided into variable-sized partitions, allowing processes to occupy the memory based on their requirements. It requires efficient management to avoid fragmentation.
Paging: Memory is divided into fixed-size pages, and programs are divided into fixed-size blocks called pages. Pages are loaded into available page frames in the main memory. Paging simplifies memory management but may incur some overhead due to page table lookups.
Segmentation: Memory is divided into variable-sized segments that correspond to logical divisions of programs. Each segment represents a different type of data (code, data, stack, etc.). Segmentation provides flexibility but can lead to external fragmentation.
Memory Allocation Strategies: Memory allocation strategies determine how memory is allocated to processes. Common strategies include:
First Fit: Allocates the first available memory block that is large enough to accommodate the process.
Best Fit: Allocates the smallest available memory block that is large enough to accommodate the process. It helps minimize internal fragmentation.
Worst Fit: Allocates the largest available memory block, leaving behind larger free blocks. It can help reduce external fragmentation.
Buddy System: Allocates memory in powers of two. If a block is not an exact fit, it is split into two halves recursively until an appropriate size is obtained.
Slab Allocation: Allocates memory in fixed-size units called slabs, suitable for data structures such as caches or kernel objects.
Memory Management Unit (MMU): The Memory Management Unit is a hardware component responsible for translating virtual memory addresses to physical memory addresses. It handles memory protection, virtual memory mapping, and page table management.
Memory Paging and Swapping: Paging involves dividing the virtual address space of a process into fixed-size pages. Swapping is the process of moving an entire process from the main memory to secondary storage when it is not currently needed. Swapping enables efficient memory utilization but incurs higher latency due to disk I/O.
Memory Fragmentation: Fragmentation occurs when memory becomes divided into small, non-contiguous chunks, making it challenging to allocate larger blocks of memory. Two types of fragmentation exist:
External Fragmentation: Free memory blocks are scattered throughout the memory, leading to inefficient memory utilization.
Internal Fragmentation: Occurs when allocated memory blocks are larger than necessary, resulting in wasted memory within a block.
Memory Protection: Memory protection mechanisms ensure that each process can access only its allocated memory and prevent unauthorized access to other processes' memory. This is achieved through techniques like access control bits, memory segmentation, and memory privilege levels.
*Operating System
An operating system is a software layer that acts as an intermediary between the computer hardware and user applications, providing an environment for managing system resources and executing programs. Here is a comprehensive explanation of operating systems:
Process Management: Operating systems manage processes, which are instances of executing programs. Process management involves:
Process Scheduling: Determining the order in which processes are executed by the CPU. Scheduling algorithms aim to optimize CPU utilization, response time, and fairness.
Process Synchronization: Ensuring proper coordination and communication between processes to prevent race conditions and data inconsistencies.
Interprocess Communication (IPC): Mechanisms for processes to exchange data and information, such as shared memory or message passing.
Memory Management: Memory management involves managing the computer's primary memory (RAM) and includes:
Memory Allocation: Allocating and deallocating memory to processes, ensuring efficient usage and preventing conflicts.
Virtual Memory: Utilizing secondary storage (e.g., hard disk) as an extension of physical memory(RAM) to allow the execution of larger programs. It involves techniques like demand paging and page replacement algorithms.
Memory Protection: Ensuring that each process can only access its allocated memory and preventing unauthorized access to other processes' memory.
File System Management: File system management involves organizing and managing files stored on secondary storage devices (e.g., hard drives). It includes:
File Allocation: Allocating disk space to files and managing file metadata, such as file names, permissions, and access controls.
Directory Management: Organizing files into a hierarchical directory structure for easy navigation and retrieval.
File Access and Sharing: Implementing file access mechanisms, file locking, and permission controls to ensure secure and concurrent access to files by multiple processes or users.
Device Management: Device management encompasses handling input and output (I/O) devices, including:
Device Drivers: Software components that communicate with specific hardware devices, enabling the OS to interact with various peripherals.
Device Allocation: Managing the allocation of devices to processes and handling device requests and interrupts.
I/O Scheduling: Optimizing the order and timing of I/O requests to maximize device utilization and minimize latency.
User Interface: Operating systems provide user interfaces (UI) to interact with the system. This can be in the form of:
Command-Line Interface (CLI): Users input commands through a text-based interface.
Graphical User Interface (GUI): Users interact with the system through graphical elements like windows, menus, and icons.
Web-based Interfaces: User interfaces accessed through web browsers, often used in client-server or cloud-based systems.
Security and Protection: Operating systems implement security mechanisms to protect the system and user data. This includes:
User Authentication: Verifying user identities through passwords, biometrics, or other authentication methods.
Access Control: Enforcing permissions and access rights to files, resources, and system functionality.
Security Auditing: Monitoring and logging system events to detect and investigate security breaches or unauthorized activities.
Error Handling and Fault Tolerance: Operating systems handle errors and ensure fault tolerance through techniques like:
Error Detection and Recovery: Detecting and recovering from hardware or software errors to maintain system stability.
Backup and Recovery: Performing regular backups and implementing mechanisms to restore system and data integrity in case of failures.
*Main components of Computer
- Central Processing Unit (CPU): The CPU, or processor, is the brain of the computer. It performs calculations, executes instructions, and coordinates the activities of all other hardware components. It consists of the following key elements:
Control Unit: Manages the execution of instructions and controls the flow of data.
Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations.
Registers: Small, high-speed memory locations used for temporary storage of data and instructions.
- Memory: Memory refers to the storage systems in a computer. The main types of memory are:
Random Access Memory (RAM): Provides temporary storage for data and instructions that the CPU needs to access quickly. RAM is volatile, meaning its contents are lost when power is turned off.
Read-Only Memory (ROM): Contains firmware or software instructions that are permanently stored and cannot be modified. It holds the computer's boot instructions. ROM chips are inserted into dedicated slots on a computer's motherboard or integrated into specific components of various electronic devices.
Cache Memory: Small, very fast memory located near the CPU. It temporarily stores frequently accessed data to reduce memory access times.
- Storage Devices: Storage devices are used for long-term storage of data and programs. Common storage devices include:
Hard Disk Drives (HDD): Use rotating magnetic disks to store data.
Solid-State Drives (SSD): Use flash memory to store data. SSDs are faster, more durable, and consume less power than HDDs.
Optical Drives: Use lasers to read and write data on CDs, DVDs, and Blu-ray discs.
USB Flash Drives: Portable storage devices that use flash memory and connect via USB ports.
Motherboard: The motherboard is the main circuit board of the computer. It provides connectivity and serves as a platform for other hardware components to communicate with each other. The motherboard includes slots for CPU, memory modules, expansion cards, and connectors for peripherals.
Graphics Processing Unit (GPU): The GPU, also known as the graphics card, handles rendering and display functions. It is responsible for processing and rendering images, videos, and 3D graphics. GPUs are especially important for gaming, video editing, and other graphically intensive tasks.
Input/Output (I/O) Devices: These devices allow users to input data and receive output from the computer. Common I/O devices include: Keyboard, Monitor, Printer, Speaker etc.
Power Supply Unit (PSU): The PSU supplies electrical power to the computer system. It converts AC power from the wall outlet to DC power required by the components.
Cooling System: Computers generate heat during operation, and a cooling system is necessary to prevent overheating. It typically includes fans, heat sinks, and sometimes liquid cooling systems to dissipate heat and maintain safe operating temperatures.
*Multimedia
Digital media is stored in binary code, where each piece of data (audio, image, or video) is represented by a series of 0s and 1s. These binary codes are stored in files on a computer's storage device, allowing the computer to interpret and present the digital media using appropriate software and applications.
Colour Format (RGB):
To represent the RGB values in binary, each component is typically assigned a fixed number of bits. For example, in 8-bit color depth, each component is represented using 8 bits, resulting in 256 possible intensity levels for each color component.
By combining different intensities of red, green, and blue, a wide range of colors can be created. For example, pure red is represented as (255, 0, 0) in binary format, pure green as (0, 255, 0), and pure blue as (0, 0, 255). Other colors are achieved by mixing different intensities of red, green, and blue.
Image File formats:
BMP: Bitmap (BMP) is a lossless image format that stores uncompressed pixel data, resulting in larger file sizes but no loss of quality.
GIF: Graphics Interchange Format (GIF) is a lossless or lossy format commonly used for simple animations or images with limited colors, supporting transparency and animation features.
JPG/JPEG: Joint Photographic Experts Group (JPEG/JPG) is a lossy format widely used for photographs and complex images, achieving significant compression while introducing some loss of quality.
PNG: Portable Network Graphics (PNG) is a lossless format supporting transparency, widely used for web graphics and images that require high-quality compression without sacrificing visual fidelity.
Audio File Formats:
WAV: WAV is an uncompressed audio file format that maintains high-quality sound but results in larger file sizes.
MP3: MP3 is a compressed audio file format that achieves significant file size reduction while sacrificing some audio quality.
OGG: OGG is an open-source audio file format that provides efficient compression and supports high-quality audio, often used for streaming and multimedia applications.
#DAY4 & DAY5, used internet for better documentation. #CS50