Introduction to computer_lec_06_fall_2018
- 1. + Dr Ramadan Babers Faculty of Science - Helwan University Fall-2018 Introduction to Computer LEC - 6
- 3. Chapter 6 Outlines Introduction What is an Operating System? Components of an Operating System 3
- 4. 1- Introduction 4 Operating system (OS) was just the basic piece of software that ruled the machine and allowed it to manipulate files. The job of the OS is to provide for an orderly and controlled allocation of the processors, memories, and I/O devices among the various programs competing for them. Sometimes, OS is defined as an Extended Machine because it presents to the user an extended or virtual machine that is easier to program and hide hardware details from the programmer.
- 5. 2- What is an Operating System? 5 The OS separates the users with their applications from the hardware of the computer. Applications programs – define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs). Users (people, machines, other computers). The Operating System controls and coordinates the use of the hardware among the various application programs for the various users. Hardware – provides basic computing resources (CPU, memory, I/O devices).
- 6. 3- Components of an Operating System 6 The main components of an operating system could be summarized in: 1) Process Management 2) Memory Management 3) File Management 4) I/O System Management 5) Protection (security) System 6) Networking (Distributed Systems)
- 7. 3-1 Process Management 7 Process Definition: is a program in execution; process execution must progress in a sequential fashion. A process may be a CPU process or an I/O process.
- 8. 3-1-1 Process States 8 As a process executes, it changes state as follows (shown in figure) 1. New: The process is being created. 2. Running: Instructions are being executed. 3. Waiting: The process is waiting for some event to occur. 4. Ready: The process is waiting to be assigned to a processor. 5. Terminated: The process has finished execution.
- 9. 3-2 Memory Management 9 Most computers have a memory hierarchy with: 1. ROM is a small amount of memory (in size) is very fast, is expensive, nonvolatile cache memory 2. RAM Hundreds or thousands of megabytes medium-speed, medium–price, volatile main memory
- 10. 3-2 Memory Management (Cont.) 10 Most computers have a memory hierarchy with: 3. Hard Disk HD Hundreds or thousands of gigabytes slow, cheap nonvolatile disk storage NB: Volatile here means that: we lose data if we shut down the device (computer or mobile) Nonvolatile here means that: we did not lose data if we shut down the device
- 11. 3-2 Memory Management 11 It is the job of the operating system to coordinate how these memories are used. The part of the operating system that manages the memory hierarchy is called the Memory Manager.