1. PROCESS MANAGEMENT DEFN OF PROCESS – A PROGRAM UNDER EXECUTION, WHICH COMPETES FOR THE CPU TIME & OTHER RESOURCES

2. CPU Switch From Process to Process

3. Diagram of Process State

4. PROCESS CONTROL BLOCK (PCB) * OS MAINTAINS INFORMATION OF EACH PROCESS IN A RECORD OR DATA STRUCTURE CALLED PCB

5. EACH USER PROCESS HAS A PCB. IT IS CREATED WHEN A USER CREATES A PROCESS & IT IS REMOVED FROM THE SYSTEM WHEN THE PROCESS IS KILLED. ALL THESE PCBs ARE KEPT IN MEM RESERVED FOR THE OS.

6. PROCESS CONTROL BLOCK (PCB) PROCESS – ID PROCESS STATE PROCESS PRIORITY REG SAVE AREA FOR PC, IR, SP PTR’ TO PROCESS MEM PTR’ TO OTHER RESOURCES LIST OF OPEN FILES ACCOUNTING INFORMATION CPU TIME CONNECT TIME etc OTHER INFORMATION IF REQUIRED BFD OF (CURRENT DIR etc) PTR’ TO OTHER PCB’

7. Ex: OS MAINTAINS 4 Q’ OR LISTS OF RUNNING PRS RDY PRS BLOCKED PRS & FREE PCB’

8. PROCESS ID PRIOR PROCESS STATE PSW CPU REGS EVENT INFORMATION MEM ALLOCN RESOURCES HELD PCB PTR DHAMDHARE

11. OPERATIONS ON A PROCESS CREATE A PROCESS KILL A PROCESS DISPATCH CHANGE PRIORITY OF A PROCESS BLOCK A PROCESS TIME –UP WAKE – UP

12. CREATE A PROCESS BEGIN 0 READ CUST – FILE ADD ….. 7 DIV…… 8 ………. 9 CALL “SORT” 10 ADD……….

13. 1 ALL CPU REGS ARE SAVED BEFORE A NEW CHILD PROCESS IS CREATED & A PCB IS ALLOCATED TO IT. 2 THE OS CONSULTS LIST OF FREE PCBs’ & ACQUIRES A FREE PCB. PCB NO 8 IN FIG. 3 ASSIGNS PID = 8 FOR NEW PROCESS 4 UPDATES FREE PCB HEADER 1 9

14. 5 OS COUSULTS IM FOR LOCN… OF SUB – PROGR.. ( STARTING ADDRS etc) 6 OS CONSULTS MM TO DET AVAIL ABILITY OF FREE MEM & ALLOCATES THOSE LOCNS 7 OS REQUESTS IM TO LOAD THE PROGR IN THE ALLOCATED MEM LOCNS 8 PRIORITY

15. 9 PCB FIELDS OF PCB 8 ARE INITIALIZED 10 OS LINKS THIS PCB IN THE LIST OF RDY PROCESSES. ROUND ROBIN (13,4,14,7,8) PRIORITY – etc PRESUMING HIGHEST PRIORITY RDY- 8,13,4,14,7

16. 5 OS COUSULTS IM FOR LOCN… OF SUB – PROGR.. ( STARTING ADDRS etc) 6 OS CONSULTS MM TO DET AVAIL ABILITY OF FREE MEM & ALLOCATES THOSE LOCNS 7 OS REQUESTS IM TO LOAD THE PROGR IN THE ALLOCATED MEM LOCNS 8 PRIORITY