Revision cards for Computing iGCSE

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revision for iGCSE
Jack Warner
Flashcards by Jack Warner, updated more than 1 year ago
Jack Warner
Created by Jack Warner over 4 years ago
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Resource summary

Question Answer
How many bits in a byte? 8
What does HTML stand for? Hypertext mark up language - a text based system for defining web pages
What is Binary? A system of number using only two digits 0 and 1 (also called the base-2 system), unlike the decimal (or denary) system in everyday use that that uses ten (base-10)
Why does data need protecting? Lots of personal/sensitive data. Have confidence in companies holding data. Protect against hackers.
What does ASCII stand for? American Standard Code for Information Interchange
What is a Variable? Space for a single piece of data, each variable has a data type. You can change variables once they have been set.
What is Boolean? A data type, can be either true or false and requires only one bit of storage.
What is a String? A data type, stores any number of characters, such as a person's name, address and postcode.
What is Malware? A piece of software that is hostile or intrusive. Examples are viruses, spyware, trojan horses and ad ware.
What is Phishing? An attempt to gain personal information (name, address, credit card details...). Usually through email.
What is RAM (Random Access Memory)? 3 letters associated with volatile memory. Generally any information stored with in this type of memory will be lost after the power is switched off.
What is Encryption? A method of scrambling data with a key code which makes data unintelligible.
What is a Pixel? The smallest element of a bitmap image.
What is an Algorithm? A sequence of unambiguous instructions to complete a task.
What is Hardware? The physical components of a computer system.
What is Software? The programs or instructions on a computer system.
What is Data? numbers, characters or symbols that have no context or meaning.
What is a LAN? Local Area Network. A network over a small geographical area.
What is a Central Processing Unit (CPU)? Brain of the computer that performs instructions.
What is an Input? Device used to input data into a computer system (e.g. keyboard, mouse, microphone, scanner, touch screen).
What is an Output? Device that outputs information (such as sound, images, video, print outs) from a computer system to the user (e.g. monitor, printer, projector, speakers, printer).
What is a PDF file? Portable document format - a file standard that displays a document accurately on any computer platform.
What is a Program? A stored set of instructions for a computer to execute.
Serial communication Bits are sent one signal at a time over a single wire .
Parallel communication Signals (bits) are sent simultaneously over a number of parallel wires.
Simplex transmission Data travels in one direction only.
Duplex transmission Data can travel in both directions simultaneously using two cables.
Half-Duplex transmission Data can travel in both directions along a single cable, but not simultaneously.
Bit rate and Baud The speed of data is measured in bits per second (bps) The Baud rate is the rate at which the signal changes Baseband means one signal (bit) is sent at a time down a serial connection In standard baseband, bit rate = baud rate.
Bandwidth The amount of data that can be carried at one time.
Parity bits A bit that is either 1 or 0 to make the digits odd or even depending on the request.
Check digit A digit at the end of a string of numbers designed to check for mistakes in input or transmission.
What does Modem stand for? Modulator/Demodulator.
What is TCP (Transmission Control Protocol)? • Breaks up messages sent over the Internet into small chunks called packets • Reassembles the packets at the other end • Detects errors • Resends lost messages.
What is IP protocol? Routes the individual packets between sender and recipient.
What is HTTP (hypertext transfer protocol)? It is used for accessing and receiving web pages in the form of HTML files on the Internet • The protocol requests the web server to upload the requested web page to the user’s browser for viewing.
What is HTTPS (hypertext transfer secure protocol)? It encrypts the information so that it cannot be hacked.
IP addressing • Every computer and other device connected to the Internet has an IP address • E.g. 81.101.137.12 • Packets are labelled with the sender’s and the destination IP addresses • Packets are sent across the Internet separately via different routes and reassembled at the end.
Network Interface Cards • Built into every networked device • Wired or wireless.
MAC addressing • A Media Access Control (MAC) address is assigned to each Network Interface Card (NIC) by the manufacturer • Your computer may have more than one MAC address, e.g. one for ethernet and one for wireless • And a mobile phone may have two different MAC addresses – one for wireless and one for bluetooth • A MAC address looks like this: 3B:14:E6:39:0A:2C.
Parts of a web address www.abc.co.uk/images/logo.jpg • Hosted on the WWW • Name of the organisation • A Company • UK based • Folder location and filename on the site
Domain Name System (DNS) • DNS technology allows you to type a name such as google.co.uk into your web browser • It translates the web address google.co.uk into an IP address • e.g. www.google.co.uk = 74.125.131.94.
DNS servers • There are 13 DNS “root” servers worldwide which keep a complete database of all names and IP addresses • Other DNS servers lower down the hierarchy hold parts of the database • When a DNS server receives a request not in its database, it will pass the request on to another server until it reaches one with the matching name and IP address • Lower level DNS servers are owned by ISPs.
Cookies • A cookie is a small data file that a server will put on a client computer • Next time the client accesses the same server, the cookie file will also be sent, identifying the client • This would explain why: • You get automatically logged in to a website • You see online adverts relevant to you and your recent searches • Website preferences are saved
The client and the server • The client is a web browser such as Internet Explorer, Chrome or Firefox • The server is responsible for serving the web pages depending on the client/end user requirement.
The role of a browser The user types a web address (URL) into the browser’s address bar • The client (i.e. the web browser) forwards this request to the server to access the web page • The server acknowledges the request and sends the HTML source code for the web page to the client • The client receives the page source code and renders it into a viewable web page.
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