Resources

• Hardware Resources
• Printer
• Processing unit
• Memory allocation
• Disk
• Software Resources
• A function
• A global variable

Flow

1. Process requests a resource and wait
2. Process uses the resource once it's available
3. Process frees the resource for usage by other processes

Types

• Preemptive
• The resource can be released gracefully by the OS (external scheduler)
• E.g., memory: if the process is interrupted, the memory stays reserved for this process to when it's resumed
• Non-preemptive
• The resource cannot be released gracefully by the OS (external scheduler)
• The resource can only be released by the holding process itself
• E.g., printer: the paper would be stuck in the middle of the impression