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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15.1 Processors, Parallel Processing and Virtual Machines
#### Type of Processor ##### Reduced Instruction Set Computers (RISC) - Uses simple instructions - Uses fixed length instructions - Instructions only require one clock cycle - Uses many registers - Makes use of pipelining - Hardwired CU ##### Complex Instruction Set Computers (CISC) - Uses many instruction formats - Uses variable length instructions - Makes use of different addressing modes - Uses few registers - Has a large instruction set - Requires complex circuits - Frequently uses cache - Instructions (converted to sub-instructions that) may require many clock cycles - Programmable CU | RISC | CISC | | ------------------------------------------------------------ | ---------------------------------------------- | | RISC has fewer instructions | CISC has more instructions | | RISC has many registers | CISC has few registers | | RISC's instructions are simpler | CISC's instructions are more complex | | RISC has a few instruction formats | CISC has many instruction formats | | RISC usually uses single-cycle instructions | CISC uses multi-cycle instructions | | RISC uses fixed-length instructions | CISC uses variable-length instructions | | RISC has better pipelineability | CISC has poorer pipelineability | | RISC requires less complex circuits | CISC requires more complex circuits | | RISC has fewer addressing modes | CISC has more addressing modes | | RISC makes more use of RAM | CISC makes more use of cache/less use of RAM | | RISC has a hard-wired control unit | CISC has a programmable control unit | | RISC only uses load and store instructions to address memory | CISC has many types of instructions to address | ##### the use of pipelining in Reduced Instruction Set Computers (RISC) - Pipelining allows several instructions to be processed simultaneously /concurrently. - .. therefore, increasing the CPU instruction throughput / the number of instructions completed per unit of time. - Each instruction stage / subtask is completed during one clock cycle - No two instructions can execute their same stage of instruction / subtask at the same clock cycle. - .. e.g., while one instruction is being decoded, the next instruction can be fetched, etc. ##### the process of pipelining during the fetch-execute cycle in RISC processors - Instructions are divided into subtasks / 5 stages - ... Instruction fetch / IF, Instruction decode / ID, operand fetch / OF, opcode/instruction execute IE, result store / write back result / WB - Each subtask is completed during one clock cycle - No two instructions can execute their same stage at the same clock cycle - The second instruction begins in the second clock cycle, while the first instruction has moved on to its second subtask. - The third instruction begins in the third clock cycle while the first and second instructions move on to their second and third subtasks, respectively, etc. | | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | | IF | 1.1 | 2.1 | 3.1 | 4.1 | 5.1 | 6.1 | | | | | | | | ID | | 1.2 | 2.2 | 3.2 | 4.2 | 5.2 | 6.2 | | | | | | | OF | | | 1.3 | 2.3 | 3.3 | 4.3 | 5.3 | 6.3 | | | | | | IE | | | | 1.4 | 2.4 | 3.4 | 4.4 | 5.4 | 6.4 | | | | | WB | | | | | 1.5 | 2.5 | 3.5 | 4.5 | 5.5 | 6.5 | | | ##### characteristics of massively parallel computers - A large number of computer processors / separate computers connected together - ... simultaneously performing a set of coordinated computations collaborative processing - network infrastructure - communicate using a message interface / by sending messages. ##### Four categories of computer architecture used in parallel processing ###### Single Instruction Single Data (SISD) single instruction single data, computer architecture which uses a single processor and one data source. ###### SIMD many/array processors execute the same instruction using different data sets ###### MISD many processors (using different instructions) use the same data set ###### MIND many processors (using different instructions) using different data set ##### virtual machine - The emulation of a computer system / hardware and/or software - ...using a host computer system. - Using guest operating system(s) for emulation. ###### Benifits - New system can be tried on different virtual hardware - without need to purchase the hardware - Easier to recover if software emulating the new computer causes system crash - as VM provides protection to other software - Emulate programs for the new computer system that are not compatible with the host computer / operating system - by using the guest operating system on the old computer - More than one new computer system can be emulated - this allows multiple operating systems to coexist on a single computer - There are security benefits // Trying a piece of suspicious software and if it is / has a virus, it will only infect the virtual machine. ###### limitation - Virtual machines may not be able to emulate the new hardware - because this hardware may have been developed since the virtual machine was developed - Using virtual machine means execution of extra code // A virtual machine might not be as efficient // resources e.g. memory or processor time are shared - processing time increased // performance degrades - Use of a virtual machine increases the maintenance overheads - because both host system and the virtual machine must be maintained
Theo
2025年5月30日 13:35
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