CHAPTER 2 TOPICS The abstract model of computing

CHAPTER 2 TOPICS ØThe abstract model of computing ØResources ØProcesses and Program

� Operating system mechanism as storage, processing data and execution element. � Resources available for build up the operating system and its functionality. � Memory as storage device for operating system � Processing life cycle for data processing. � Student able to explain the basics mechanisms of operating system. � The basic processes of OS and its resources.

� programmer views a computer as a mechanism that can access, transform and store information. Fundamental unit of Computation Fundamental unit of Information Process A sequential file is a named, linear stream of bytes of memory.

� Resources � Traditionally, the most common resource is a file. A process must request a file before it can read it or write it. Further, if the file is unavailable, the process must wait until it becomes available. � Files � A sequential file is a named, linear stream of bytes of memory. You can store information by opening a file creating an abstract file resource description and assigning a name to it and then writing a block of bytes into the file. Similarly, you can access information stored in a file by opening the file and reading the block of bytes stored in the file.

� Resource is any abstract machine component, including file, that a program must have explicitly allocated before it can execute the program. � When resources unavailable, process will discontinue/blocked until become available. monitor File Resources Keyboard Processor Memory Tape drive

� Processor- most obvious resource the process requires. � Memory-Computer data storage(program may request and reference all needed memory when process come into existence. � Tape drive-To read info from magnetic tape, the drive must be allocated to the processer prior to the tapes’ being mounted and read.

�A process is a sequential program in execution. Component of process: 1. Code-object program to be executed 2. Data-which program will execute, obtained from file 3. Resources-require by program(file contains requisite info) 4. Status-process execution

� Program- Static entity made up of program statements that define process behaviors when executed on some set of data. � Process- Dynamic entity that executes the program on a particular set of data using resources supplied by the system

Component of process: 1. Code 2. Data 3. Resources 4. Status