What is OS?
OS is an Operating System, which interacts with the system software and hardware instead of user, where user is not required to understand the system hardware in order to use the system.
Services Provided by an OS -
- Program Execution
- Memory Management
- Process Management
- File System Management
- I/O Device Management
- Security Access Control
- Resource Management
- Time Management
- Error Detection
- Communication Services
Process Execution
The OS runs the application which is installed in the system.
Memory Management
OS is responsible for Allocating and Deallocating for processes.
Process Management
OS tells the Program to run first and till how much - multitasking(creating and sheduling of processes only).
File System Management
Managing and organizing of of file in the system.
I/O Device Management
Devices like Mouse, keyboard scanner and so on are managed by OS.
Security and Access Control
Protects from unauthorized access of data, manages the permission controls of other software.
Resource Management
manages the resources like CPU, RAM and other hardware and assigning of processes is done.
Time management
keeps timer for the running processes to stop or wait for execution of programs.
Error Detection
Detects Hardware and Software errors and handles it. errors like software crashing or disk failure.
Communication service
Helps interact processes to each other for performing specific tasks.
Types of OS
Batched OS
runs multiple jobs gives us batch output and does not interact with the user. Output comes after all jobs(programs that needs to be executed) are done.
Time-Sharing OS
shares CPU time among multiple user or tasks. multiple users use the OS at the same time, but actually the system is switching them very fast.
Distributed OS
this is multiple computer acts as a single computer. Manages tasks across all nodes.
Network OS
Computer working together in the same network(LAN) using Network OS(independent), share file and user management.
Real-Time OS
system where needs instant respond and are reliable. system will be very fast as the OS is build for real-time decision-making.
RAM and ROM (types of memory)
RAM(Random Access Memory)
it is also known as main memory, it is a fast processer. information stored or executed in this is temporary(Volatile Memory), if power goes off then the information stored is also gone.
ROM(Read Only Memory)
it is a non-volatile memory(permanently stored, and is not lost when turned off). the contents of the ROM is written by the manufacturer while manufacturing.
SCRAM and DRAM (Types of RAM)
- Static RAM - its like a cache memory of the RAM. it is faster and more reliable compared to other RAM. it does not need refreshing, more expensive and needs more power.
- Dynamic RAM - mainly used as main memory, its is used to store data, in the form of bit capacitors value 1(charged) and 0(discharged). needs to be refreshed to retain data.
(Types of ROM)
- Programable ROM(PROM) - can be reprogramed.
- Erasable ROM(EROM) - can be erased by UV light and reprogramed.
- Electrically Erasable ROM (EEROM) - can be erased and reprogramed electrically.
- Mask ROM - programed during manufacturing only.
Virtualization
using of a whole hardware(extra power, ram and other things) typa sht on the current system OS using software like hypervisors. example - VM ware
Containerization
running of a specific app/web app isolated from the OS on a container. example - Docker
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