9618 Computer Science
AS Content
Chpater 1 Information representation
1.1 Data representation
1.2 Multimedia
1.3 Compression
Chapter 2 Communication
2.1 Networking
2.2 The internet
Chpater 3 Hardware
3.1 Computers and their components
3.2 Logic Gates and Logic Circuits
Chapter 4 Processor Fundamentals
4.1 Central Processing Unit (CPU) Architecture
4.2 Assembly Language
4.3 Bit manipulation
Chapter 5 System Software
5.1 Operating Systems
5.2 Language Translators
Chapter 6 Security, privacy and data integrity
6.1 Data Security
6.2 Data Integrity
Chpater 7 Ethics and Ownership
7.1 Ethics and Ownership
Chapter 8 Databases
8.1 Database Concepts
8.2 Database Management Systems (DBMS)
8.3 Data Definition Language (DDL) and Data Manipulation Language (DML)
Chapter 9 Algorithm Design and Problem-solving
9.1 Computational Thinking Skills
9.2 Algorithms
Chapter 10 Data Types and Records
10.1 Data Types and Records
10.2 Arrays
10.3 Files
10.4 Introduction to Abstract Data Types (ADT)
Chapter 11 Programming
11.1 Programming Basics
11.2 Constructs
11.3 Structured Programming
Chapter 12 Software Development
12.1 Program Development Life cycle
12.2 Program Design
12.3 Program Testing and Maintenance
A2 Content
Chapter 13 Data Representation
13.1 User-defined data types
13.2 File organisation and access
13.3 Floating-point numbers, representation and manipulation
Chpater 14 Communication and internet technologies
14.1 Protocols
14.2 Circuit switching, packet switching
Chpater 15 Hardware
15.1 Processors, Parallel Processing and Virtual Machines
15.2 Boolean Algebra and Logic Circuits
Chapter 16 Operating System
16.1 Purposes of an Operating System (OS)
16.2 Translation Software
Chpater 17 Security
17.1 Encryption, Encryption Protocols and Digital certificates
Chpater 18 Artificial intelligence (AI)
18.1 Artificial Intelligence (AI)
Chapter 19 Computational thinking and problem solving
19.1 Algorithms
19.2 Recursion
Chapter 20 Further programming
20.1 Programming Paradigms
20.2 File Processing and Exception Handling
Mr. Theo
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5.1 Operating Systems
## operating system (OS) ### Need for OS - The hardware is unusable without an OS // hides complexity of hardware from user - Acts as an interface/ controls communications between user and hardware / hardware and software // or by example - Provides software platform / environment on which other programs can be run #### Provision of a user interface: - Allows a user to communicate with the hardware // vice-versa - ... by making navigation around the system easier - Provides facility for user inputting data - Provides facility for outputting to the user - Command line / Graphical User Interface ### Key Management Tasks #### (Main) Memory Management - Controls the movement of data between RAM, processor. - Allocates memory to processes - Ensures fair usage of memory - Organises memory - Keep processes separate - To release memory when a process stops - Makes use of virtual memory #### File Management - defining the file naming conventions - performing specific tasks such as create, open, close, delete, rename, copy, move. - maintaining the directory structures - ensuring memory allocation for a file by reading it from the HDD/SSD and loading into memory #### Security Management - Provide /upgrade firewall / anti-malware - Makes provision for recovery when data is lost - Provides usernames and passwords / encryption / user accounts - Prevents unauthorised access - Ensures privacy of data #### Hardware (input/output/peripherals) Management - Use of device drivers - Installation of appropriate driver software - Controls access to data being sent to/from hardware/peripherals - Controls access to hardware/peripherals - Manages communication between devices / hardware and software #### Process Management - Decides which process to run next - Supports multitasking - Allocation of processor time - Scheduling of processes or tasks / multi-tasking / multi-programming etc. - Resolution of conflict when two or more processes require the same resource ### utility software - To help users to set-up / configure / analyse / optimise / maintain the computer ... - .. by for example, making memory allocation more efficient - ... by for example, checking the system for faults ##### Backup software - Creates a copy of the contents of a disk / partition. Can be set up to automatically backup // schedules backups - Allows the user to decide what is backed up, e.g. all data // all files that have changed since the last backup - Allows the user to set up an off-site backup - May encrypt the backup files - Restores the data if necessary ##### Virus checker - Scans files stored on a computer system for malicious code - Scans files when they enter the system / memory stick inserted / download etc - Sets up a schedule for virus-checking - Isolates / quarantines / deletes viruses - Regularly updates the virus definitions ##### Defragmentation - Make individual files occupy contiguous blocks // move free space together - Improve disk access times // Data/files can be loaded faster - Finds files that are split across the disk - ...and moves the blocks that make up each file to be contiguous - Collates free space ##### File compression - Reduces the file size - ...by using algorithms to change the data - ... which can be either lossy or lossless ##### Disk content analysis - used to check disk drives for empty space and disk usage by reviewing files and file folders. - can lead to optimal use of disk space by removal of unwanted files and downloads ##### Disk Formatter - removing existing data from a disk that has been used previously - setting up the file system on the disk - partitioning the disk into logical drives if this is required. ##### Disk repair software - Allows disk to report errors (e.g. “bad sector”) - Restore the functionality of a damaged or corrupted disk - Preventing data loss and ensuring the proper operation of the storage device. ### Program libraries - Set of pre-written / pre-compiled / pre-tested subroutines - ... which can be called in other programs - by installing/importing the library ##### Benefits - Saves (programming/testing) time as code does not have to be written/re-written from scratch // code does not have to be tested - Code is already tested so it is more robust/likely to work - If there is an improvement in the library routine the program updates automatically - can perform complex calculations that the programmer may be unable to do ##### Drawbacks - Compatibility issues - ...may not work with the other code/may require changing program for it to work - Not guaranteed thorough testing - ... may be unknown or unexpected bugs / virus - Library routine may not meet exact needs - .. may give unexpected results //. may need editing - If library routine is changed - ... there may be unexpected results / errors #### Dynamic link library files - DLL - A collection of self-contained (shared library) programs that are already compiled - Linked to the main program during execution - Library program code is separate from the EXE file - Library file only loaded into memory when required at run time - A DLL file can be made available to several applications (at the same time) - If DLL routine is updated the program that uses it will run the update ##### Benefits - (main) memory requirements for program is reduced - .. as dynamic link library is loaded only once / when required - the executable file size of the program using the DLL will be smaller - ...because the executable does not contain (all) the library routines - maintenance not needed to be done by the programmer - ...because the DLL is separate from program - no need to recompile the main program when changes are made to DLL - ... because changes / improvements/ error correction to the DLL file code are done independently of the main program - A single DLL file can be made available to several application programs - ..Saving space in memory / easing the pressure on memory ##### Drawbacks - The executable code is not self-contained ... - ... the DLL file(s) needed to be included at run time. - Appropriate (linking) software must be available at run-time ... - ... to link/include / import the DLL files. - The DLL file must be present ... - ... otherwise (unable to find X.dIl) errors - Unexpected changes to the DLL file / corrupted DLL file ... - ... could mean the program stops working as expected - Malicious changes to the DLL file ... - ... could install a virus on the user's computer / related files could be corrupted
Theo
2025年5月30日 13:26
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