Processes

What is a Process

• talking about programs executing but what it is meant?
• At the very least, we are recognizing that some program code is resident in memory and the CPU is fetching the instructions in this code and executing them
• Of course, a running program contains data to manipulate in addition to the instructions describing the manipulation. Therefore, there must also be some memory holding data.
• We are starting to talk of processes or tasks or even jobs when referring to the program code and data associated with any particular program
  • a program in execution,
  • an instance of a program running on a computer,
  • a unit of execution characterised by a single, sequential thread of execution,
  • a current state an associated set of system resources (memory, devices, files),
  • process execution must progress in sequential fashion
• An operating system executes a variety of programs:
  • Batch system, jobs
  • Time-shared systems, user programs or tasks
• Keep track of the states of every process currently executed. make sure; no process monopolises the CPU, no process starves