WJEC GCSE Computer Science

1. Computer systems

1. Computer systems

What 4 parts of the computer does the CPU connect to?

ports

RAM

Storage

What two parts make up a computer system?

Hardware and software

What is Hardware?

Physical parts that make up a computer system

What is software?

The code that makes the computer run

What is the data bus used for?

Communication between the RAM and the CPU

What is the address bus used for?

Communication between the RAM and Storage

What is the Ethernet port used for?

Internet

What is the USB port used for?

Transfer data

What is the DVI port used for?

Just video transfer

What is the HDMI port used for?

Video and sound transfer

What is the Audio port used for?

Audio transfer

How does Input devices work in a computer system?

Input data into the computer system

What is the main reason for Process's in a computer system?

inputted data is converted into a readable form

What do Output devices do in a computer system?

Show the processed data to the user

List some input devices

Keyboard

Mouse

Joystick

Microphone

Scanner

Graphics tablet and stylus

Bar code recognition

Optical mark recognition

Sensors

What are the advantages and disadvantages of a Graphics tablet and stylus?

+

More natural

Greater accuracy and precision

-

Expensive

Hard to select and click on items

Large

What are the advantages and disadvantages of a Bar code recognition scanner?

+

Fast

Shows error

can change price easily

-

Products have to be entered in to database

If system fails they don't work

What are the advantages and disadvantages of a Optical mark recognition scanner?

+

Very fast

Accurate

-

Can't analysis human errors

No text

Needs special paper and stationary

List some output devices

Inkjet printer

Laser printer

Plotter

Speakers

Headphones

Monitor

Projector

What are the advantages and disadvantages of a inkjet printer?

+

Cheap

Small

Good quality prints

-

Loud

Slow

Small cartridges

Page can come out wet

What are the advantages and disadvantages of a laser printer?

+

High quality print out(not wet)

Fast

Can do lots of printing

-

Expensive

Complex and expensive to repair

Large

What are the advantages and disadvantages of a plotter?

+

Very high quality

Can print out large pictures

-

Slow

Expensive

List some input and output devices

Voice activated systems

Multi-touch gestures (touch screens)

Whats the 5 purposes of the CPU?

Control input output devices

Synchronise data

Logical decisions

Calculation

Sorting and searching for data

Explain the fetch execute cycle

Data is fetch for by the CPU

This data is the decoded by the CPU

This data is the executed by the CPU

What does a controller do?

Controls fetch execute cycle

What does the arithmetic logic unit (ALU) do?

Logical decisions

Calculation

What do registers do?

Fast temporary storage inside CPU

What does internal memory do?

Used by the CPU like ram

What do buses do?

Transfer data

How does the clock speed affect a PC?

How fast the fetch execute cycle is carried out

How does the number of cores affect a PC?

Allow multitasking

Performance

Amount of processors

How does the cache-memory affect a PC and what is it?

High speed memory next to CPU

Improves performance with more

How does the cache-disk affect a PC and what is it?

Data stored in RAM

Improves performance with more

How do different types of processors affect a PC?

64 bit - Fast can hold 1TB of RAM

32 bit - Slow can hold 4GB of RAM

What is ROM?

Read only memory

Non- volatile holds operating system

What is RAM?

Random access memory

Volatile stores data closer to CPU to increase performance

What is virtual memory?

Where the hard disk is used temporarily as RAM

What is a magnetic disk and what are it's advantages and disadvantages?

1 and 0 are assigned as magnetic fields for storage

+

High storage

Fast

Strong

-

Expensive

Not portable

What is magnetic tape and what are it's advantages and disadvantages?

1 and 0 are punched in to tape for storage

+

High storage

Cheap

-

Slow

Fragile

What is a CD and what are it's advantages and disadvantages?

1 and 0 are burned to the surface by a laser for storage

+

Portable

Cheap

-

Low storage

Fragile

Slow

What is a SSD and what are it's advantages and disadvantages?

Data is compressed and composed into a series of logic gates

High storage

Fast

Portable (USB) or Not portable (SSD

Strong (SSD) or Fragie (USB)

Expensive

What is cloud storage and what are it's advantages and disadvantages?

Storing data on a external sever accessible by the internet

+

High storage

Accessible anywhere

-

Requires internet

Could be hacked

Speed depends on internet speed

What does a modem do?

Allows data to be transferred over a phone network

What does modulation mean?

Converts data in to analogue

What does de-modulation mean?

Coverts analogue into data

2. Data represation

What does ASCII stand for?

American standard code for information interchange

What is ASCII?

7 bit code that can hold 128 characters

What is Unicode?

16 bit code that can hold 65,536 characters

What is a truth table?

Shows all possible logical inputs and there associated outputs

What does a NOT gate do and what does it look like?

I-_

-------I _IO-------

I-

Gives the oppisite

What does a AND gate do and what does it look like?

Like a D with two inputs and one output

Only provides a 1 if two 1 are present

What does a OR gate do and what does it look like?

Like a banana with two inputs and one output

Gives a 1 if a 1 is present

Put 200 into binary

1100 1000

Put 79 in to hexadecimal

4F

What is a Character and how big is it?

1 byte and stores a character

What is a Integer and how big is it?

4 bytes and stores a whole number

What is a Real and how big is it?

8 bytes and stores a decimal number

What is a Boolean and how big is it ?

1 byte and stores True or False

What is a String and how big is it?

1 byte and stores a character which is pieced together with other characters to form a word

What is a bit ?

Either 1 or 0

What is a nibble ?

4 bits

What is a byte?

8 bits

What is a kilobyte?

1024 bytes

What is a megabyte?

1024 KB

What is a gigabyte?

1024 MB

What is a terabyte?

1024 GB

What is a petabyte?

1024 TB

What is a exobyte?

1024 PB

What is a zettabyte?

1024 EB

What is a yottobyte?

1024 ZB

How does a CPU decode a byte?

The first nibble in the operator (instruction) and the second nibble is the operand (data)

How does the CPU keep track of instruction?

By updating its program counter

Where does the CPU hold these instruction?

In the main memory

How is sound recorded?

Analogue is changed into binary to represent the curve

What is the sampling rate and what is it measured in?

Hz and how many sound samples are taken per second

What does a higher sampling rate give?

Smoother sound

What id the sampling resolution?

Audio bit depth

What does a high sampling resolution give you?

High quality recording and a large sound range

What is a pixel?

The smallest dot on a image

What is metadata?

The information on the images height, width and colour depth that comes in the file

What is resolution?

Amount of pixels per inch

What is colour depth?

Amount of bits per pixel

How many colours does 1 bit per pixel give?

2... Black and white

How many colours does 8 bits per pixel (1 byte) give?

256 colours

How many colours does a 16 bits per pixel (2 bytes) give?

65536 colours

3. Computer software

What is a operating system?

A software that controls hardware and creates a user interface to run software

What are the 5 main parts of a operating system?

User interface

Multitasking

Peripheral management

Memory management

Security

What is a GUI

Graphical user interface

What makes a GUI so easy to use?

Windows and Icons (make it use to use) Menu and Pointers allow easy navigation.

WIMP

Who does a GUI suit and where is it used?

On a home or business computer. Suits a range of ability

What is a CLI?

Command line interface

Who uses a CLI and what for?

Advanced programmers.. to create new programs/coding

Whats a MDI

Menu driven interface

Who uses a MDI?

Machines like ATM and self checkout

Why are MDI useful?

There are only limited options

Easy to understand (users cant get lost)

Users cant break into the system

What 3 things does memory management control?

RAM

Cache

Virtual memory