Multi Processing/ Multi Programming/ Multi Tasking/ Multi Threading

✅ Multi Processing

several CPUs

• each CPU can execute different task

• parallel processing

• in process, work in parallel
• operate multiple jobs at the same time

• 👍🏻 reduce time

• 🛠️ used in cloud
• 🛠️ multi-core

✅ Multi Programming

multiple programs are loadad into memory
CPU switches between them

• ⭐️ several program in memory
• OS schedule which program to be run
• CPU switching

• 👍🏻 Optimize CPU usage

• 🛠️ run text editor and compiler simultaneously

💡 Paging https://soheeparklee.github.io/posts/OS-12paging/

✅ Multi Tasking

OS execute multiple tasks simultaneously
extension of multiprogramming, but more general sense

• Task: unit of work in OS/ command for work
  
• process보다 확장된 개념
  
• CPU switching

• appears that CPU is executing two tasks at the same time

• OS handles multi tasking
• tasks have independent memory, do not share resources
• need IPC for communication between tasks

• 👍🏻 has independent memory, can be executed memory

• cooperative multitasking

• preemptive multitasking: force CPU switch

• 🛠️ modern OS, run web browser, text editor, music player
• general purpose OS
• run multiple Apps

✅ Multi Threading

multiple thread in one process

• threads share resource like memory, but execute independently

• 👍🏻 data sharing among thread

• 👍🏻 efficient communication

• 🛠️ multiple client requests