Single-Tasking Systems

Older systems like MS-DOS allowed only one process at a time. You had to wait for a process to finish before starting the next.

Process Flow:

1. Process created in memory
2. Process starts running
3. Process finishes execution
4. System becomes free for next command

Problem:

If a process performed an I/O operation, the CPU would sit idle, wasting resources.

Multi-Programming Systems

Multi-programming allows multiple processes to exist in RAM (besides the OS), ensuring the CPU always has something to work on.

Multi-programming vs. Multitasking:

• Multi-programming: Several programs in memory; CPU picks one that’s ready.
• Multitasking: A form of multi-programming with time-sharing:
  • Each process gets a time slice
  • CPU preempts processes when their time is up
  • Processes resume from where they left off

Process States (Five-State Model)

1. New