Class PPT

Classification of OS

OS can be categorized based on the target system (computers).

• Mainframe systems
• Desktop systems
• Multi-processor (Parallel) systems
• Distributed systems
• Hand-held systems
• Real-time systems

Resident Monitor

• Early (oldest) OS resides in memory and monitor execution of the programs. If it fails, error is reported.
• OS provides hardware interfacing that can be reused by all the programs.

Batch Systems

• The batch/group of similar programs is loaded in the computer, from which OS loads one program in the memory and execute it. The programs are executed one after another.
• In this case, if any process is performing IO, CPU will wait for that process and hence not utilized efficiently.

Multi-Programming

• In multi-programming systems, multiple program can be loaded in the memory.
• The number of program that can be loaded in the memory at the same time, is called as "degree of multi-programming".
• In these systems, if one of the process is performing IO, CPU can continue execution of another program. This will increase CPU utilization.
• Each process will spend some time for CPU computation (CPU burst) and some time for IO (IO burst).
  • If CPU burst > IO burst, then process is called as "CPU bound".
  • If IO burst > CPU burst, then process is called as "IO bound".