What does this say? Je ne parle pas Français ainsi je ne peux pas comprendre ceci ! ! I don't speak French so I can't understand this!! =
Languages and Translators
Computers only understand 1s and 0s
This is called machine code .
It is very hard for people to read and understand
Instead of trying to write machine code, we use high level languages to program.
What does a high-level language look like?
PRINT “PLEASE ENTER YOUR AGE” INPUT AGE PRINT “YOU ARE “: AGE Short Instructions like sentences Made up of English words
High-level languages are portable .
They can be translated into many different versions of machine code
Machine code is not portable as it only works for a certain processor
PRINT “PLEASE ENTER YOUR AGE” INPUT AGE PRINT “YOU ARE “: AGE Translator 01010110 01010110 01010110
Translators take the high-level language and translate it into machine code.
They work like human translators
J'aime l’informatique PRINT “HELLO” I like Computing 0011 1110 0011 translate
Summary Computers only understand 1s and 0s, which we call machine code . Humans write programs in high level languages because they are like English, and can be translated into machine code. High level languages can be portable which means they can be translated into different kinds of machine code .
An operating system controls all the tasks the computer does for you
Reads in data from keyboard and mouse Sends text and graphics to the screen Sends data to your printer
Loads data into the memory from the Hard Disk
Saves your files to disk
Examples of Operating Systems
Apple Mac OS X
But NOT things like:
These are programs that run on the Operating System
Types of File
There are two different types of file:
Program files , which are files full of instructions that the system runs. Microsoft Word is a program file.
Data files, which are used by programs. A Microsoft Word document (like a letter you wrote and saved) is a data file.
H C I uman omputer nterface
Human Computer Interface
The Operating System provides the HCI for the user
User uses mouse to click icons
Operating System translates into instructions
What was clicked?
What should be done now (load file, save file, load program)?
Types of Operating System
Computer reacts to user requests immediately and processes the data
Example: Internet ticket booking (Travel, Concert)
What would happen if the system wasn’t interactive?
User clicks on link to buy ticket
System checks immediately if there is a ticket available
Ticket is booked for the user
Types of Operating System
Real Time System
Real time systems react even faster than interactive systems
Designed to always process the right amount of information in time
This means the Real Time system is instant every time
Used in spaceship control systems, nuclear reactors…..
Where else would Real Time Systems be used instead of Interactive Systems?
Summary Operating systems control the tasks the computer does for the user. This includes loading data into memory, reading data from they keyboard and mouse, saving files and sending text and graphics to the screen or printer. There are two types of file - program files (such as Microsoft Word) and data files , that are used by program files (such as a letter your wrote in Microsoft Word) We interact with the OS through the Human Computer Interface (HCI). The OS translates the keyboard and mouse presses into instructions and performs actions such as loading and saving files. Interactive operating systems are used when users need immediate feedback. Real-time operating systems are used when systems always need instant results (such as a control system on a plane).
Check your understanding
What kind of system would you use for the following (choose from background, interactive and real-time):
Flight booking web site
Controlling a robot?
On a home computer?
Running a nuclear reactor
Interactive Real-Time Interactive Real-time
What jobs does the Operating System do?
Give an example of an Operating System?
What are the 2 types of file?
What does the HCI do?
When would Interactive Processing be used?
When would Real-Time Processing be used?
It is very wise to organise your files!
Lots of files in the one place = hard to organise
Group them in directories
The Operating System sorts our data using directories (often called folders) and files.
Low Level Machine
We now know about Operating Systems, High Level Languages, and how we access data.
Now we are going right inside the computer to look at how the CPU and memory works
The two most important parts of the inside of the computer are the CPU and memory. The CPU (Central Processing Unit) is the “brain” of the computer where the computer works things out. The memory is where the computer “remembers” things for the CPU.
The Computer’s Memory
Computers use main memory and backing storage to store data.
Main memory is the fast memory inside a computer that stores data the CPU is currently using
Backing store is the bigger but slower memory that stores files and programs for the computer
Backing store comes in two types – magnetic and optical.
Magnetic – Hard Disk and Floppy disk
Optical – CDROM and DVD
Inside the computer there is main memory
Main memory is made up of memory chips
There are two kinds of main memory:
RAM – R andom A ccess M emory
ROM – R ead O nly M emory
Random Access Memory
RAM is where the computer stores data that is it currently using. This includes:
Data from the keyboard as you type
Data from open files and programs you are using
When you turn off your computer, all the data in RAM will be lost .
This is why you must always save files to backing store before turning off a computer!
Read Only Memory
ROM is READ ONLY – you can’t change it
It is written in the factory when the computer is made
The computer can read the data in the ROM straight away when the computer is switched on
This is why parts of the OS are sometimes stored on ROM
It isn’t wiped when the computer is switched off
A good way to remember the difference between RAM and ROM is to think that RAM is like a notebook and ROM is like a textbook.
With RAM you write in what you need to remember
With ROM it is already there and you don’t change it!
How to measure memory
We said before that everything in a computer is either a 1 or a 0
This is because computers use binary numbers
The size of memory is usually given in megabytes or gigabytes , but what does that mean?
Memory size So an iPod with 60GB of storage space has: 60 x 1024 x 1024 x 1024 x 8 = 515,396,075,520 bits! (over 515 billion bits…)
The processor is the brains of the computer
A processor takes data in , processes it and then outputs the data to screen or printer.
Input Process Output mouse calculation Print out Display on screen keyboard
Some real world examples of IPO…..
Check your understanding…
Give a real life example of IPO
Give a computer example of IPO
Explain why you can not store data in ROM
What happens to RAM when the computer is switched off? Why should this be ok?
B I N A R Y
We count in “decimal”
We have 10 fingers, so it makes sense that we group by 10s I.e. 1, 10, 100, 1000, 10 000 etc
Computers count in binary
They use different columns and group by twos I.e. 1, 2, 4, 8, 16, 32, 64, 128
We count to 10:
A computer would do this in binary:
Binary numbers have a power of 2, and decimal numbers (that we count with) have a power of 10. Let’s go back in time……
If computers can only work with binary numbers, how do they store words and pictures etc?
Since computers only use binary, they have a binary code for each character
This code is called ASCII
American Standard Code for Information Interchange
Let’s try some ASCII conversion….
ASCII Table http://www.ascii.cl/htmlcodes.htm
The size of a text file Hello The eagle has landed! How many bytes would these files take up?
Text is stored in the computer using ASCII codes
Each character’s ASCII code is
8-bits, i.e. 1 byte in size
So, we can work out the storage
requirements of text files
A graphic can be a drawing, graph, painting or photograph.
Graphics are made up of a grid of pixels .
A pixel is a single point on the screen.
In black and white graphics, the grid of pixels can be represented by binary numbers
1 stands for a black square, 0 stands for a clear square.
Each pixel takes up 1-bit to store.
How many bits do you think it will take to store this graphic? The grid is 8 x 8 pixels, so it will take 64 bits to store. 64 bits is 8 bytes.
To store colour graphics, we need to assign each colour a different number e.g. red = 1, blue = 2 etc.
These colour codes are stored in binary
The larger the binary number, the more colours we can have. How many do we need?
32-bit graphics are normal (4.3 billion different colours)
Systems task 9
10 minutes on Systems Task 9, page 25
If finished, go onto Knowledge Check 5
Computers store text and graphics in binary.
They use a code called ASCII (American Standard Code for Information Interchange)
Each character has a code in ASCII
Black and white graphics are stored by using 1 bit for each pixel (1 for black, 0 for white).
We can work out the size of these graphics by multiplying the width of the graphic by the height.
Colour graphics use more bits for each pixel depending on how many colours are needed.
We’ve covered how the CPU works, and what the Operating System software does
Now let us look at hardware for the computer
The chip is made of layers of silicon crystal wavers on which very small electronic components are installed.
Backing storage memory is used to store files when the computer is switched off, and are usually removable.
There are two types of backing storage, Optical and Magnetic . We’ll look at magnetic first.
Tape Drive Tape drives take large plastic tapes which store data in binary using magnetic ‘spots’ to encode the data They have a large capacity, and fast data transfer rates Tapes wear over time so need to be stored in suitable environment and are suited to medium and short term storage DAT tapes can hold up to 200 Gigabytes so are used for backup
Floppy Disks are made from circular plastic plates coated in iron oxide (which is a magnetic chemical).
Data is stored on the surface as patterns of magnetic spots.
Floppies are small and compact
They store up to 1.44Mb of data (about 1/3 of an MP3 file)
They can be damaged easily by dust, dampness, electro/magnetic pulses
Hard Drive Hard drives store data by writing magnetic patterns onto metal disks. The surfaces are divided up into sectors and tracks which allows each part to be accessed directly.
The disk is in a sealed box to prevent dust damage.
The read/write head is just above the surface of the disk
The disk spins between 7,000 and 10,000 rpm
They hold gigabytes of data (most recently up to 750GB in size)
Optical Backing Storage
Optical backing storage uses laser optics to read and write data.
Data is stored in binary by using lasers to burn microscopic marks on the disk surface.
Data is read by reflecting light off the surface to read the microscopic marks.
High Capacity - 650 Megabytes
Stores data in microscopic grooves
Works in the same way as CD-ROM
Stores more data because it uses a narrower laser beam to read and write to disk
Ordinary DVDs hold 4.7 Gigabytes
Double-sided, multilayered DVDs store up to 17GB
Enough space for large files such as movies
Stands for Compact Disk Recordable
Uses a layer of dye which laser changes to store data
CD-Rs are WORM - W rite O nce R ead M any
Once files are written on, they can’t be deleted or changed
CD-Rs are read-only after they are written
Stands for Compact Disk Re-writable
Unlike CD-R, these can be rewritten
This is because they use the laser to change the reflective properties of microscopic marks
CD-ROMS, CD-Rs and CD-RWs are used for:
backing up large files
Storing large multimedia presentations
Storing large programs, like games
CD-ROMS, CD-Rs and CD-RWs are slower than hard disks
But they are removable!
DVD-R and DVD-RW
Works in the same way as CD-R and CD-RW
Stores more data because of narrower laser
Can store up to 4.7GB
USB Flash drive
USB Flash drives are rewritable memory chips
Store data just like a disk
Used as backup and plugs into USB ports on a computer
Very small and portable
Sizes from 64MB to 2 Gigabytes
Input devices are pieces of hardware that let you control a computer by sending data to the computer from your device.
Mouse A mouse lets you control the pointer on screen, and click to select icons. Mice usually have 2 buttons and sometimes a scroll wheel.
Trackball A trackball is similar to a mouse except the ball is on top. The trackball does not move around the desk like a mouse. They are useful when a user does not have desk space to move a mouse, and for people who find it hard to use their arms to move objects around.
Trackpad A trackpad is a small pad that senses the movement of your finger. It lets you control the mouse by moving your finger across the pad. You can click by tapping the trackpad.
Graphics Tablet Graphics Tablet A flat plastic panel with electronic sensors below the surface detect the movements of a pointing device. Very accurate – used by graphic artists / designers / Computer Aided Design (CAD)
Touch screen Touch Sensitive Screen Simple to operate Useful for public information systems Tiring to use after a while Not precise
keyboard Keyboard Input text and numbers Function keys QUERTY layout Very common, nearly every computer has one
Scanner Scanner Input drawing, photographs from paper. Light beam passes over page and a sensor detects the reflection Optical Character Recognition (OCR) software can recognise writing
Digital cameras Digital Cameras
Digital Cameras 2 Digital Cameras Captures light coming through the lens and stores a digital image Allows instant review of picture taken Delete photos you don’t like Takes a memory card – can be various capacities.
Digital cameras 3 Choosing a camera Look at the accuracy (resolution) – measured in Megapixels. 5 Mpx is enough Does it have a zoom lens? Digital zoom is worthless because it produces poor pictures What capacity is the memory card?
Video camera Digital Video cameras Same principle as still digital cameras Need a large storage capacity – video takes up a lot of space (15 frames per second) Some have a small LCD screen to view your video Features: zoom, focus, lighting, infrared recording, onboard editing
Webcams Webcams Same principle as digital video camera Connected directly to computer via USB Can put a webcam in a website Useful for video calls via MSN Messenger
Laser printer Laser Printer
Uses a laser beam to copy image of a page onto light-sensitive drum
Ink (toner) attracted to the drum then transferred to paper
Laser printers are fast
The output is high quality
They are expensive to buy but relatively cheap to maintain.
Inkjet printer Inkjet Printer Sprays ink onto the paper Printout quality is high Cheap to buy, can be expensive to maintain (expensive ink) Slower than Laser Printer
Plotter Plotter Uses inkjet technology to produce large, accurate and complex drawings Used by architects / designers Quicker than drawing by hand
Monitor Monitor Screen used to display computer output Different monitors have different resolutions The higher the resolution, the more detailed the picture will be High resolution needed for CAD and art work
TFT / LCD LCD / TFT Displays LCD = Liquid Crystal Display These screens have the following advantages: Flat, light, needing little power, can be run from a laptop battery The one disadvantage is that sometimes they are not bright enough and can cause eye strain
TFT / LCD 2 LCD / TFT Displays TFT = Thin Film Transistor Same advantages as LCD. Uses a tiny transistor to form each pixel Can update the image very quickly, allowing it to handle complex graphics and animation which LCD displays cannot
Speakers Computer Speakers Produce sound from the computer Allow you to do multimedia presentations, video-conferencing, games, music etc Computer speaker systems vary in quality and number of speakers depending on output wattage (RMS) or surround sound capability etc
Desktop VS Laptop
Desktop VS Laptop
Desktop computers stay in the same place. Laptop computers are portable
Because of this, the components used need to be light and consume less power (run off battery)
This means that a laptop with the same specification (CPU speed, RAM) will cost more than a same spec desktop.
Laptop computers are small and compact
They weigh a lot less than a desktop – usually 1.5 – 3 kg
Runs off battery, charges from mains
Has a flat screen (LCD or TFT)
Has a normal keyboard and trackpad
Is about the size of your hand
Small keyboard or a stylus with handwriting recognition
Stores data on a memory card
Useful for ultra-portable computing on the move
Store contacts, calendar, editing documents, email etc
Large and powerful
Lots of processing power (multiple CPUs) and RAM
Many users connected using terminals
Used by banks and other large businesses to process and store data
Multimedia systems integrate sound, animation, video and graphics
Most modern computers have these capabilities
Interactive learning, information systems, multimedia web pages, games
A fast CPU and lots of RAM and storage
Quality TFT display
Digital camera (video)
Surround sound speakers
A good system for viewing and creating multimedia might include: