OCR GCSE Computer Science Paper 1+2 Content

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What is a computer?

An electric, PROGRAMMABLE DATA PROCESSING machine.

What is a system?

A collection of PARTS that work TOGETHER for a COMMON PURPOSE.

What is a computer system?

A collection of HARDWARE and SOFTWARE working together to create a CODED SOLUTION. It involves a set of inputs being processed to present a set of outputs.

Why are computer systems everywhere?

Because:

• Versatile

• Small

• Cheap

What is a program?

A set of INSTRUCTIONS that the computer carries out to process data.

What is an Input?

PROVIDES DATA for further processing

What is a process?

Where the input is MANIPULATED in order to process meaningful information.

What is an output?

Where the information is PRESENTED to the user in a suitable format.

What is a System Boundary?

A system that is SEPARATEs from the outside world so it separates what is in a system from what is not.

What is an Interface?

A device or program enabling a user to communicate with a computer. Interconnections between systems.

Give 3 examples of computer input devices

• Mouse

• Keyboard

• Scanner

Give 3 examples of computer processes

• Searching

• Calculations

• Graphing

Give 3 examples of computer output devices

• Screen

• Speaker

• Projector

LIst reasons of why computer systems are important:

-Communication (Emails, Social networks) -Retail (E-commerce)

• Improved quality in manufacturing - Cheaper manufacturing

• Faster access to information

• Improves quality of life (E.g. Bionics for people without limbs)

• Safety ( Emergency response, guiding aircrafts, monitoring patients)

• Education

• Business

Name 6 types of computer systems

• General-purpose systems

• Dedicated systems

• Control systems

• Embedded systems

• Expert systems

• Management information systems

What is a general purpose system?

Designed to perform multiple tasks- a WIDE VARIETY of purposes. Various applications can loaded.

Give examples of general purpose system.

Desktops, Laptops, Smartphones

What are the advantages of general purpose systems?

• Very popular

• Cheap

• Well tested

• Wide support (Easy to use)

• Not specific to a particular user (E.g. Microsoft)

• Capable of development into tailor-made software

What are the disadvantages of general purpose systems?

• Very basic

• Low quality

What is a dedicated system?

Produced for a FIXED SYSTEM - perform a single function or set of functions E.g. A Ticket vending machine at a train station ( Only has one purpose, not designed to do anything else)

What the advantages of dedicated systems?

• Has complete control of the dedicated server.

• Makes the server very :

• Secure

• Stable

• Powerful

• Extremely reliable

• Saves a lot of money on infrastructure

• Hardware equipment maintenance and replacement is taken care by the web hosting server provider

What are the disadvantages of dedicated systems?

• Expensive

• Needed knowledge to use it completely

What is a control system?

Computer systems that CONTROL MACHINERY, rather than produce an output for humans to respond to. E.g. Central heating systems, Traffic light systems

What are the advantages of control systems?

• Can operate 24 hours without taking breaks

• Will accurately repeat actions over and over again

• Can process data from sensors very quickly

• Can take account of hundreds of inputs at the same time

• Make accurate and reliable decisions

What are the disadvantages of control systems?

• The software for this system is specialist so it will cost a lot of money to develop

• If computer malfunction, the system won't work

• If there is a power cut , the system will not work

• Can't react to unexpected events as it only responds in the way it has been programmed

What is an embedded system?

Computer systems that are part of a LARGER SYSTEM- forms a part of an electric device. Include portable devices e.g. MP3 players, cameras Include larger installations e.g. Traffic lights, Controllers of machinery in factories

What are the advantages of embedded systems?

• Cheap

• Small size

• High reliability

• Fast

• Easy to manufacture

• Fewer interconnections

What are the disadvantages of embedded systems?

• Hard to maintain

• Doesn't evolve with the technology improvements

• Hard to transfer files from one machine to another

• Hard to back up embedded files

What is an expert system?

Computer systems that are designed to BEHAVE like HUMAN beings - An application that mimics the knowledge and experience of a human expert. (Designed to provide reasonable answers when given a set of conditions about a problem in hand.)

What are the three main component parts of an expert system?

• Knowldge base (Database of facts)

• Inference engine (Software that makes deductions using the knowledge base)

• An interface ( Allows a human user access to the system)

What are the common uses of embedded systems?

• Diagnosing diseases

• Finding faults in a machine

• Financial services

• Engineering designs

What are the advantages of an expert system?

• Expert advice available all the time

• Can be used as a training aid to increase expertise of staff

• Makes rational decisions without emotion

• Does not get overworked

• Efficient way of getting answers

What are the disadvantages of an expert system?

• Only covers a narrow range of knowledge

• Time consuming and Expensive to make a good expert system

• Not as good as having human experts

• Does not learn from mistakes unless there is user feedback and human maintenance

• Unlikely to come up with creative solutions

What is a management information system?

It BRING INFORMATION TOGETHER from all parts of an organisation.

What do management information systems cover?

• Technology

• Data

• People

Give examples of a management information system?

• School management information systems (Deal with administration, teaching and learning)

• Office Automation system (Automate workflow and maximize the efficiency of data movement.)

What are the advantages of a management information system?

• Minimizes information overload

• Brings co-ordination

• Makes control easier

• Facilitates planning

• Assembles, processes, stores, retrieves, evaluates information.

What are the disadvantages of a management information system?

• Highly sensitive, so it requires constant monitoring

• Budgeting is extremely difficult

• Lack of flexibility to update itself

• Effectiveness decreases due to frequent changes in top management

What is reliability?

HOW DEPENDABLE a system is to do the job you entrust it with.

Why are reliable systems needed?

Because they play a central part in life or death situations:

• Aircrafts navigation and control

• Railway signalling

• Many medical situations

What can mistakes in a design and production of systems lead to?

• Expensive errors

• Data loss

• Compromised privacy

• Down time

How is reliability improved?

Testing is designed to uncover errors

What is data integrity?

Data being ACCURATE and CONSISTENT throughout its life.

How can data integrity be affected?

• Human errors

• Software bugs

• Viruses and other malware

• Hardware malfunctions

• Natural disasters

• Errors that occur when transmitting data from one computer to another.

How can these risks be reduced?

• Backing up data regularly

• Controlling access to data via security mechanisms

• Using error detection and correction software when transmitting data.

Why can testing never be complete?

• Software is too COMPLEX

• Testing is EXPENSIVE

• TIME consuming

What are standards in a computer system?

Conventions and rules which are usually defined by a responsible organisation.

What do standards exist for?

• Programing languages

• Operating systems

• Electrical interfaces

• Communication protocols

• Data formats

Why are standards important?

Because they :

• Ensure quality control

• Maintenance

• Enable equipment from different manufactures to work together

• Make learning new system easier because they have similar characteristics

• Minimise waste

• Help ensure fair play and access to markets

Name the 5 different examples of standards

• De facto standards

• De jure standards

• Proprietary standards

• Industry standards

• Open standards

What are the De Facto Standards?

• Develop through COMMON USAGE.

• Important because they ensure files and systems can be used by anyone. E.g. Microsoft Word - De facto standard for supplying word processed documents

What are De Jure Standards?

• LAW - Systems must adopt as they have become so universally accepted that they have to be adhered or else communication is impossible E.g. ASCII, Unicode, HTML, PDF

What are Proprietary Standards?

• Owned by an organisation

• Ensure compatibility between the company's products E.g. Apple Iphones and Macbooks using the apple software. Windows software standard owned by Microsoft

What are the advantages of proprietary standards?

• Can be used to reduce competition from rival products

• Look and feel familiar to users so this will speed up learning new systems

• Improved reliability

• Maintained well

What are Industry Standards?

• Set by non-commercial organisations

• ANSI (America National Standards Institution) - Set standards for programming languages

• ISO (International Standards Organisation) - Produces international standards for :

• Engineering

• Agriculture

• Medicine

• IT Many standards relate to hardware & allow easy interconnections between devices: E.g. USB (Universal serial bus)

What are Open Standards?

• Standards that are PUBLICLY AVAILABLE.

• Software can be modified by users

• Source is in the public domain

• Updated by a community of developers and they act quick to fix problems

• Very high quality

Ensures that access to resources is not dependent upon:

• A single application or a particular hardware platform

Give examples of Open Standards

• HTTP

• www (World wide web)

• HTML

What are the ethical considerations when creating computer systems?

• Privacy

• Terrorism

• Copy right

• Data security

• Espionage

• Access to sensitive data

• Fair charging for services

Give examples of Laws that manufacturers must follow when creating a new computer system.

• Copy Right

• The Data Protection Act (1998)

• Protects people's privacy

• Contains safeguards

• The Computer Misuse Act (1990)

• Illegal to gain unatuhorised access to computer systems

• Illegal to modify the data stored in them

Why is it beneficial for manufactured goods to be produced by robots rather than humans?

Because:

• They are made to a greater accuracy then humans thus are better quality products that last longer

• More energy efficient

Why do obsolete computers have to be disposed?

Because they contain toxic materials. Then the E-waste goes to landfills where the toxic chemicals can leach out into the soil.

List methods of how to reduce energy consumption

• Virtual servers reduce the number of physical servers in a data center

• Solid State Storage uses less energy than rotating disk drives

• Automatic standby by switching turns computers off when not in use

• Modern screens that are less energy intensive than other monitors

What is hardware?

The PHYSICAL components of a computer system.

What components do hardware contain?

Input, output processing and storage devices.

What is the computer architecture?

The internal logical structure and organisation of the computer hardware.

Which architecture is the basis for all modern computers?

VON NEUMAN architecture.

Where are all of the instructions and data stored in the same place as?

Binary numbers

What is the CPU?

The CENTRAL PROCCESSNG UNIT It is the hardware within a computer whose purpose is to PROCESS DATA.

Describe the fetch-execute cycle..

1. FETCH the instructions from the memory

2. DECODE the instructions to find out what processing to do - sorts instructions into parts for specific parts of the CPU

3. EXECUTE the instruction. E.g. Mathematical calculations may be performed.

What are the two main components of the CPU?

• The arithmetic and logic unit (ALU)

• The control unit

What does the ALU do?

It carries out all the arithmetic and logical operations such as addition. subtraction and logical operations

What does the control unit do?

Uses electrical signals to control flow of data in the CPU

What is the purpose of the CPU?

• Control the movement of data and instructions

• Fetch data and instructions from memory

• Decode and execute instructions

• Perform arithmetic operations such as add and subtract, and logical operations such as AND, NOT, OR

What is Cache memory?

It is HIGH SPEED memory attached to the CPU

What does the cache memory do?

It stores the FREQUENTLY ACCESSED instructions and data so that they can be accessed quickly. E.g. Web-browser GOOGLE uses cache

Why is it good to have more cache?

Because the larger the cache means that more data can be stored which can later be accessed quickly (Helps long term performance)

What is the Boot Sequence?

It is a sequence of processes that contains all the information and instructions to get the computer running.

What does the boot sequence contain?

It contains the BOOT LOADER which is a program that starts the sequence when the computer is switched on.

Where is the boot sequence stored?

It is stored in the ROM so the CPU knows where to find it easily, and load & execute the first program.

What is a Operating system in the CPU?

It is a system that provides the programs for the CPU to process.

What does the speed at which CPU processes data depend on?

• CPU clock speed (Processing speed)

• Cache memory

• The number of cores

What is Clock Speed?

It is how many cycles can be completed per second (Hertz)

What happens if the clock speed is faster?

The faster the cycles can be completed , the more instructions can be executed per second which improves the efficiency and performance of the CPU. BUT it will run hotter and will consume more energy.

What is a clock chip?

An electronic clock chip in a computer that controls the timing of signals so it determines the speed of the fetch-execute cycle.

What is Overclocking?

It is adjusting the clock to run faster than the CPU is really designed for. BUT this makes the CPU run hotter so extra cooling fans also have to be purchased

What are multi-core processors and what do they do?

Multi-core processors use multiple CPUs working together. They allow multiple instructions to be executed simultaneously. Therefore the more number of cores the higher the performance level.

What is a virtual core?

It splits one core between 2 processes - Dividing your time between 2 jobs at a time

What is in the main memory and primary storage of a CPU?

Random Access Memory (RAM)

What does the RAM do?

It stores data, application and operating system whilst in use.

What are the features/ characteristics of RAM?

-VOLATILE (Data lost when power is turned off ) thus cannot be used to permanently save any files.

• Has QUICK read/write times so things can be accessed and stored quickly ( Faster than anything stored in secondary storage)

• Contains the OPERATING SYSTEM

• LARGE (4GB or more in typical computers)

• Stores all of the data associated with programs that currently open so programs are quicker to run than if they were stored on the hard drive (which is a slower form of storage)

• MORE RAM = MORE PROGRAMS can be open at the same time

Name the type of memory that stores the boot sequence

Read-Only Memory (ROM)

What does ROM do?

A store of data in a computer that cannot be overwritten.

What are the features/ characteristics of ROM?

• NON-VOLATILE (Data is always available and is not lost when the computer is turned off) -Stores instructions and data required to START UP the computer ( Form of storage that contains pre-recorded data i.e. the boot sequence)

• The data storage cannot be altered & can only be read.

• Programmed during computer manufactoring

• SMALL (1 or 2MB required for boot program)

• Used in simple devices e.g. Calculators as they don'thave too many uses.

What is Virtual Memory and what does it do?

• It is part of the hard drive used as an EXTENSION to RAM.

• Used when all the RAM has been used up

• Data in the RAM that has not been accessed recently (e.g. a program left open for a while) is sent to be STORED TEMPORARILY.

• Virtual memory accessed far SLOWER as hard dive have a slow read/write time.

What happens to virtual memory if there is more RAM?

Adding more RAM REDUCES the use of virtual memory and improves the performance of the computer

What is Flash Memory?

• TYPE OF ROM that can be overwritten.

• Type of NON-VOLATILE MEMORY using SOLID- STATE technology.

What is flash memory used for?

Used as a removable, PORTABLE medium for storing and transferring data e.g. USB, Camera memory stick.

What are Solid-State Drives (SSD)?

It is technology based on electronics with NO MOVING parts, mechanical parts. SSDs can contain MORE DATA and will eventually replace hard disks as they are QUICK and have HIGH CAPACITY.

What is a bus?

It is a part of the computer that TRANSFERS DATA and signals between the components of the computer.

What is the Motherboard?

The central Printed Circuit Board (PCB) that holds the crucial components of the system.