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CHAPTER 1: INTRODUCTION TO OPERATING SYSTEM., CHAPTER 2 : MEMORY AND…
CHAPTER 1: INTRODUCTION TO OPERATING SYSTEM.
1.1.1 Define of operating system - An operating system software that manage computer system hardware.
1.1.2 Describe the various type operating system software: i) Monolithic - an module can call any other module without any reservation. ii) Layered - breaks up the operating system into different layers. iii) Microkernel - components in microkernel directly with one and other. iv) Networked and distributed - A software program that controls other software and hardware that run on a network.
1.1.3 Describe various Architecture operating system
a) Single processor system - in single processor system only one process can run at time other process must wait until the CPU become free.
b) Multiprocessor system - A multi-core processor is a single computing component with two or more independent central processing unit.
c) Clustered system - allows 2 or more system to share storage.
1.1.4 The various product of operating system:
i) Closed source operating system are owned by someone and distributed through a variety of retail channels.
-Example of closed source are window 7,8,10, windows server 2008 and 2004
ii) Open source software is computer software with its source code made available with a license.
1.1.5 Concepts in relation to operating system: a) Multitasking
b) Multiprogramming
c) Time sharing
d) Buffering
e) Spooling
f) Catching
1.1.6 Components of operating system: a)Kernel - one program that running at all
b) Shell - the command line- interprated and control statements is executed automatically
c) File system- allow data to be stored located and retrieved easily.
Interface: 1.1.7 a) Command line- common iinteprated
b) Voice Acurated - controlled by means of the human voice ( example: microsoft voice command for PDA
c) Graphical user interface - interface allows provides a mouse based window- and- menu system as an interface
d) Wev form - web form on a web page allows a users to enter data that is sent to a server for processing.
1.1.8 Application Programming interface (API) - - An application program calls the function to request the services.
An API is a set of functions provide by an operating system or other system software.
CHAPTER 2 : MEMORY AND PROCESS MANAGMENT
Memory managment : --computer available pool of memory
allocating space to application routines and making sure that they do not interferce with each other.
Function of memory manager: (keep trap) a)Primary function of memory to preserve the space main memory occupied by the operating system
b) check the validity of each request fpr memory space.
Main memory: -for program to be accessed by the CPU the operating system loads them into RAM and also main memory can directly accessed by the CPU.
Example of main memory: - RANDOM ACCESS MEMORY (RAM)
READ ONLY MEMORY (ROM)
Memory management strategies: i) FETCH- virtual memory manager to determine when a page is copied from disk to memory.
ii) PLACEMENT- virtual memory manager to determine where the pages to be loaded.
-first fit ( allocate the first free block that is large enough for the new process)
best fit ( allocated the smallest block among those that are larger enough for the new process)
-worst fit ( allocate the largest block among those that are large enough for the new process)
iii) REPLACMENT - determine which virtual page must be removed from memory to make room for new page.
Resident routines - programs as they run. (example; routine that control physical I/O.
Transient routines - stored on disk and read into memory only when needed (example: routine that formats disks)
Swapping Technique: ( temporarily remove a process from the memory of a computer system.
-SWAP-OUT OPERATION: by copying its instruction and data onto a disk.
-SWAP-IN OPERATION- by loads another process in this area of memory
Segment Table & Address Translation -d is displacement ( offeset) of the memory location from the start of segment. Limit is length that specifies the sizes of the segment.
Paging - under paging a program is broken into fixed -length pages.
Major system resource types within a computer system.
-CPU time is amount of time which a central processing with CPU.
Memory refers to physical devices used to stored program sequences of instructions or data
Hard Disk Space the amount of permanent storage of data measured in bytes.
-Network is a group of two or more computer system linked together.
-Throughput number of process that complete their execution per time unit
Electrical power is the rate at which electric energy is transfer by an electric circuit.
-External devices device that is not housed inside in the computer cabinet.
State of a process - New: created - Ready : Assign a process to a processor
-Run : instruction execution
-Blocked : for an event to occur
Terminated: finished execution
Scheduling Creteria: - CPU UTILIZATION (max) - THROUGHPUT (max)
-TURNROUND (min)
WAITING TIME (min)
-RESPONSE TIME (min)
Six process scheduling algorithms - FIRST-COME, FIRST -SERVED (non- preemptive)
SHORTEST JOB FIRST ( non-preemptive)
-PRIORITY ( non-preemptive/preemptive)
-SHORTEST REMAINING TIME ( preemptive)
-ROUND ROBIN (non-preemptive/preemptive)
MULTIPLE - LEVEL QUIUES (non-preemptive/preemptive)
CHAPTER 3 : FILE MANAGMENT
Define file managment as a system that an operating system uses to keep track of different files. (KEEP TRACK OF WHERE FILES ARE STORED)
Define of directory structure: - The way an operating system's life system and its files are display to the user.
File Access Techniques: a)SEQUENTIAL - implemend by the file system
data is accessed one record right after the last
-read pointer to be moved a head by one
writes allocate space for the record and more the pointer to the new end if the files.
b) DIRECT
-method useful for disk
-numbered sequence of blocks or records
-no restrictions on which blocks are read/ written in any order.
c)INDEXED
-index is built indicating the block containing the record with a given value for the key field. ( it is built on top of sequential access)
File Organization technique refer to the way data is stored in a file. It determine the methods of access efficiency, flexibility and storage devices to use.
4 types of directory structure: -STORAGE STRUCTURE , DIRECTORY STRUCTURE, SINGLE-LEVEL DIRECTORY AND TWO-LEVEL DIRECTORY
Storage structure in operating systems - VOLATILE STORAGE DEVICE (looses its contents when the power of the devices is removed)
-NON- VOLATILE STORAGE DEVICE (does not looses it contents when the power is removed and it hold all the data when the power is removed.)
Single- level directory ( simplest directory structure and contain same directory which make it easy to support and understand.
Two-level directory ( create a directory directly inside the root direct.
File management -ALLOCATED (hard disk and loading it into memory while updating its record of who is using what life.
-DEALLOCATES (files updating the file tables and rewriting the files to the hard disk)
DEFINITIONS; -FILED (collection of bytes that can be indetified by a user, and has a type and size.
-RECORD (collection of related filed)
-FILE (collection of records)
-DIRECTORY OR FOLDRE (special of file that which has lists of files )
Physical storage allocation: (the operating system store files as record in memory , where many record make up a single file.
-Three main ways a file is physical stored in memory:
*CONTIGUOUS STORAGE (record of a file are stored one after another.)
*NON- CONTIGUES STORAGE (records of a file are stored where ever there is free space)
*INDEXED STORAGE (records in the file, an index block is created, with pointers to each individual file)
Access control matrix ( access that each use has for each file on the system.
Possible access are:
R-read E-execute W-write D-delete
FREE SPACE LIST:
-manage records all free disk block
-to create a file, search the free- space list for the required amount to space and allocated that space to the new file.
USING BIT MAP:
-frequently free space list it implemented as a bit map
-if block free, the bit is 1
-if block allocated, the bit 0