1. C o n f i d e n t i a l 1 Course: BCA Semester: III Subject Code : BC 0042 Subject Name: Operating Systems Unit number : 1 Unit Title: Overview of Operating System Lecture Number: 1 Lecture Title: Overview of Operating System HOME NEXT

2. C o n f i d e n t i a l Unit-1 Overview of Operating System 2 Overview of Operating system Objectives To understand definitions of program, process and thread definition of operating system what are the functions of operating system HOME NEXT PREVIOUS

3. C o n f i d e n t i a l Unit-1 Overview of Operating System 3 Topic covered Introduction to Operating systems What is operating system Functions of operating system Class Summary Overview of Operating system NEXT PREVIOUS

4. C o n f i d e n t i a l Unit-1 Overview of Operating System 4 Introduction to OS What is program ? Program is sequence of instructions which tells the computer what is the task to be done. Program can be written using high level or assembly languages. The user normally uses a text editor to write their program in a high level language, such as Pascal, C, Java, etc. HOME NEXT PREVIOUS

5. C o n f i d e n t i a l Unit-1 Overview of Operating System 5 Introduction to OS What is language translators ? A software used to translate a program written in any other computer languages to machine language. A compiler is used to translate a high level language program into machine code. A assembler is used to translate a assembly language program into machine code. HOME NEXT PREVIOUS

6. C o n f i d e n t i a l Unit-1 Overview of Operating System 6 Introduction to OS What is process ? A process is a program in execution. A process is executed sequentially, one instruction at a time. A program is a passive entity. For example, a file on the disk. A process on the other hand is an active entity. A process being an active entity, changes state as execution roceeds. A process can be any one of the following states: New, Running, waiting, ready or terminated HOME NEXT PREVIOUS

7. C o n f i d e n t i a l Unit-1 Overview of Operating System 7 Introduction to OS What is thread? Thread is a single sequence stream which allows a program to split itself into two or more simultaneously running tasks. It is a basic unit of CPU utilization, and consists of a program counter, a register set and a stack space. Because threads have some of the properties of processes, they are sometimes called lightweight processes. HOME NEXT PREVIOUS

8. C o n f i d e n t i a l Unit-1 Overview of Operating System 8 What is OS ? What is operating system? Operating System is a System Software(Set of system programs) which provides an environment to help the user to execute the programs. The Operating System is a resource manager which allocates and manages various resources like processor(s), main memory, input/output devices and information on secondary storage devices. HOME NEXT PREVIOUS

9. C o n f i d e n t i a l Unit-1 Overview of Operating System 9 What is OS ? The purpose of an OS is to provide an environment in which a user can execute programs in a convenient and efficient manner. The operating system must provide certain services to programs and to the users of those programs in order to make the programming task easier, these services will differ from one OS to another. HOME NEXT PREVIOUS

10. C o n f i d e n t i a l Unit-1 Overview of Operating System 10 Functions of operating system Functions of Operating System Operating systems perform the following important functions: 1. Processor management : It means assigning processor to different tasks which has to be performed by the computer system. 2. Memory management : It means allocation of main memory and secondary storage areas to the system programmes, as well as user programmes and data. HOME NEXT PREVIOUS

11. C o n f i d e n t i a l Unit-1 Overview of Operating System 11 Functions of operating system 3. Input and output management : It means co-ordination and assignment of the different output and input devices while one or more programmes are being executed. 4. File system management : Operating system is also responsible for maintenance of a file system, in which the users are allowed to create, delete and move files. HOME NEXT PREVIOUS

12. C o n f i d e n t i a l Unit-1 Overview of Operating System 12 Functions of operating system 5. Establishment and enforcement of a priority system : It means the operating system determines and maintains the order in which jobs are to be executed in the computer system. 6. Assignment of system resources, both software and hardware to the various users of the system. 7. Provide a effective user interface The user interacts with the operating systems through the user interface and usually interested in the look and feel of the operating system HOME NEXT PREVIOUS

13. C o n f i d e n t i a l Unit-1 Overview of Operating System 13 Class Summary Introduction to Operating systems Concepts of program, process and thread What is operating system What are the Functions of operating system HOME PREVIOUS