Processes

• Classify three types of schedulers;

• Explain five types of scheduling algorithms; and

• Compare the performance evaluation of the scheduling algorithms.

Concept of Process

• A process is a sequential program in execution
• It defines the fundamental unit of computation for the computer
• Components of process are:
• Object Program – code to be executed
• Data – is used for executing the program
• Resources – while executing the program, it may require some resources
• Status of the process execution – used for verifying the status of the process execution.

Process vs Program

Process

• Is a dynamic entity i.e a program in execution
• Is a sequence of information executions
• Exists in a limited span of time
• Two or more processes could be executing the same program, each using their own data and resources

Program

• Is a static entity made up of program statements
• Contains the instructions
• A program exist at place in space and continues to exist
• Does not perform the action by itself.

Process State

• As a process executes, it changes state
• The state of a process is defined by the current a activity of that process
• The process may be in one of the following states
• New – a process that just been created
• Ready – processes waiting to have the processor allocated to them by the OS so that they can run
• Running – process that is currently being executed
• Waiting – a process that cannot execute until some event occurs such as the completion of an I/O operation
• Terminated – The process has finished execution