Computer Science topic 6 IB HL

Primary memory (RAM)

• Place where all data/programs currently being processed are kept

Secondary storage (HDD/SSD/optical drives)

Place were data/program can be stored if powered is lost (RAM is volatile)

Processor speed

- Processor does all calculations in a computer system.
-Speed is measurement of how many calculations can be done per second (1Ghz = 1 billion calculations per second)

Processor Cores

Each processor has at least 1 ALU or core. If you have 2 ALUs you can do two operations at once, etc.

Bandwidth

• Measurement of how much data can be sent at same time in a certain time frame (also called bitrate)

Screen resolution

Measurement of number of pixels in height x width of display

Sound processor

- Sound reproduction is done by a separate processor, freeing up the CPU to do other calculations.
- Can also contain a bank of 'sampled' sounds to reproduce better quality music/audio

Graphics processor

Does complex graphic processing (like 3D rendering)

Cache

Contains the instruction/data the CPU is likely to request next from RAM - it massively speeds up processing as the CPU does not have to 'wait' for instructions to arrive from RAM.

Network connectivity

Each network card connects to a particular type of network media (cable/wireless signal)

• Mainframe

Processor: Thousands of cores
Primary memory: Vast amounts Secondary memory: Vast amounts
Common use: • Used in large companies • Used for weather/financial models and predictions • Used to 'virtualize' smaller computers • Main players: CRAY/IBM

Servers

Processor: Many high spec PCs running in parallel (3-4GHz)
Primary memory: Big capacity (32GB+ per machine)
Secondary memory: Terabyte per machine
Common use: • Used to 'serve' networks • Used as data centers for 'cloud storage' • Size varies according to use

PCs

Processor: Single processor (multiple cores) 1-4 GHz
Primary memory: 2-16 GB
Secondary memory: 256 GB to 2 TB
Common use: • Used in companies/schools (where portablility is not needed) • Can be expanded by adding expansion cards (graphics cards) • Used to be the most common type of personal computer

• Cell phones

Processor: Single/Multicore
Primary memory: 1-3 GB
Secondary memory: Usually limited, but can be upgraded (MicroSD card)
Common use: • Most common personal computing device in the world • Getting more capable, rivaling PCs/laptops • Biggest constraint is screen size and input options (lack of physical keyboard)

Tablets

Processor: Single/Multicore
Primary memory: 1-4 GB
Secondary memory: Usually limited, but can be upgraded (MicroSD card)
Common use: • Very common for media consumption • Getting more capable, rivaling PCs/laptops • Biggest constraint is lack of physical keyboard

Limiting any of the following would impact the experience of the user

• Primary memory
• Secondary storage
• CPU speed
• CPU cores
• Connectivity

Multi-user system

Either many users on the same machine or many users connected to the same network

Multi-programming system

system that can have different programs installed

Single programming system

can only run one program/one set of programs

Fuctions of operating systems

- device configuration (controls peripheral devices connected to computer)
- File management (transfer files between main & secondary storage, manages file folders, allocates the secondary storage space, and provides file protection and recovery)
- Memory management (allocates the use of random access memory to requesting processes)
- Interace platform (allows the computer to run other applications)

drivers

specially written, individualised programs

Which programs control peripheral devices?

driver programs, translation programs, and other programs,
Ulitmately the user controls the peripheral devices (mouse, keyboard, printer), but the programs help in doing so.

Managing (primary) memory

- OS ensures that each program runs in its own allocated space
- could other wise cause problems with security and corruption

Virtual Memory

feature of an OS that allows a computer to compensate for shortages of physical memory by temporarily transferring pages of data from random access memory (RAM) to disk storage.

Managing (secondary) storage

- The OS manages secondary storage by providing structure and access methods to these structures
- often referred to as folder-structure, but in some OSes it is called directory structure
- OS also manages the security access of these folders

User interface

- used to interact with the computer to perform various tasks
- user gives commands to computer and enters the data
- OS translates the input/output and sends it to the correct memory address/folder address to be processed

Types of Operating Systems

- Graphical User Interface Operating systems (e.g. Windows)
- Command Line Operating System (e.g. Linux)

Interrupt Handler

- function in of the OS or a device driver, whose execution is triggered by the reception of an interrupt
- interrupts are used to handle high-priority conditions that require the interruption of current code processor is executing

Dedicated OS

An operating system that is for a specific device.
e.g. iOS 9 for iphones/ipads only, Ubuntu Kylin for Chinese users, OS for satellite TV receiver boxes

Advantages of a dedicated OS

- Security -- ensures higher level of secuity
- Customizability -- dedicated operating systems custom made to do a specific function at maximum effeciency
- Modify priorities -- can make running some devices easier to user or better suited to their audience. Custom OS means certain unneeded aspects can be removed, reducing amount of secondary memory and RAM being used.

Abstraction

when the OS hides certain hardware details from the user and applications. This means that the user cannot see changes in the hardware. Can be used to make related devices appear the same from the user's point of view.

Drive letter

- a single alphabetic character A through Z that has been assigned to a physical drive or drive partition in the computer
- All computers with a hard drrive will always have that default hard drive assigned to a 'C:' drive letter

Java Virtual Machine (JVM)

interprets compiled Java binary code (called bytecode) for a computer's processor (or "hardware platform") so that it can perform a Java program's instructions
- each platform gets its own JVM so that Java code can run on any platform