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IGCSE COMPUTER SCIENCE (THEORY) PAPER #1 EXAM QUESTIONS AND ANSWERS
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IGCSE COMPUTER SCIENCE (THEORY) PAPER #1 EXAM QUESTIONS AND ANSWERS
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IGCSE COMPUTER SCIENCE (THEORY)PAPER #1 EXAM QUESTIONS AND
ANSWERS
What is meant by data losing its value? - Answer-The more accurate and complete data
is, the more valuable it is.
If data is lost, corrupted or accidentally changed, it becomes less accurate and
complete and loses value.
What is simplex data transmission? - Answer-data sent in one direction only
What is Machine code
1st Generation language? - Answer-The 1s and 0s that make up the instructions for a
computer. This is the lowest level of programming language that all programs must be
converted to in order to be executed on a computer. Computers only understand
machine code.
Explain what is meant by an automatic backup. - Answer-An automatic backup:
is where a computer makes a backup made without user intervention
is where the computer automatically creates a backup at a scheduled time and date.
What is half duplex data transmission? - Answer-data sent in both directions but not at
the same time
What is Assembly language
2nd generation language? - Answer-One step up from machine code where the
individual machine code instructions are represented as simple keywords such as ADD
or BRA. Requires an assembler to turn it into machine code.
Explain how phishing and pharming trick a user into giving up personal data. - Answer-
Four answers accepted from:
- Phishing uses email that pretends to come from a person or organisation the user is
familiar with.
- The email asks the user to confirm account details by clicking on a link
- If clicked, the link directs the user to a fake website that looks like the organísation's
real site, where they can be tricked into giving up personal data.
- Pharming also uses fake websites to try to gain access to personal data.
- When a user tries to visit a genuine site they are instead directed to a fake site
- If the user enters personal data on the fake site the data is stolen and passed to
criminals.
What is full duplex data transmission? - Answer-data sent in both directions
simultaneously
,What is High level language
3rd generation language.? - Answer-A computer programming language that is much
closer to a human language than machine code. Examples of high level languages are
Python, PHP, Visual Basic and C (although there are lots more!). Requires and
interpreter or a compiler to turn it into machine code.
Explain how anti-virus software may help to prevent distributed denial of service attacks.
- Answer-Answers could include:
- Denial of service attacks occur when malware on a computer instructs the computer to
send a high volume of requests to a server
- Anti-virus software detects and removes malware from computers, removing the cause
of the attack.
Give an example of simplex data transmission - Answer-data being sent from a
computer to a printer
What is a Megabyte (Mb)? - Answer-1024 kilobytes.
Explain why computer security is more effective when anti-virus software and firewalls
are used. - Answer-Four answers accepted from:
- Malware is software that is designed to disrupt or modify a computer system.
- It is usually accidentally downloaded from email attachments, websites and USB sticks
- Anti-virus software detects and removes malware from a computer, helping to keep
the computer safe.
- Computers communicate by sending messages. Most messages a computer sends
are authorised
- Some messages are created by malware or hackers. These messages are
unauthorised messages
- Firewalls monitor communications to prevent unauthorised messages from being sent,
helping to keep the computer safe.
Give an example of half duplex data transmission - Answer-a phone conversation
between two people where only one person speaks at a time
What is a Gigabyte (Gb)? - Answer-1024 megabytes.
What is a Terabyte (Tb)? - Answer-1024 gigabytes.
Give an example of duplex data transmission - Answer-broadband connection on a
phone line
Describe how a proxy server can help keep data safe. - Answer-Two answers accepted
from:
- Aproxy server is a computer that sits between a network server and the internet
- The proxy server directs traffic away from the main server by examining the traffic.
,- If the traffic is authorised it is forwarded to the network server; if not, the traffic is kept
away from the network server, keeping it and the data on it safe.
Explain the difference between symmetric and asymmetric encryption. - Answer-Four
answers accepted from:
- Encryption converts data into a form that cannot be understood by anyone other than
an authorised user
- Encryption works by using a key
- Symmetric encryption uses the same key to encrypt and decrypt data.
- Asymmetric encryption uses two separate keys which work as a pair.
- The first key is used to encrypt the data.
- The second key is used to decrypt the data.
What is serial data transmission? - Answer-when data is sent, one bit at a time, over a
sing wire or channel
What is binary? - Answer-The number system we use to represent the data stored in a
digital computer. Binary is a base 2 number system and uses the digits 1 and 0.
Describe what a protocol is and how protocols help protect data. - Answer-Two answers
accepted from:
- A protocol is a set of rules that governs communications between computers.
- Some protocols, such as secure socket layer, use asymmetric encryption to create a
secure link between one computer and another.
- This means that data can be safely transmitted between computers as anyone without
the encryption keys cannot read the data.
What is parallel data transmission? - Answer-when several bits of dots are sent down
several wires or channels at the same time
What is hexadecimal? - Answer-A base 16 number system that we use to represent the
data stored in a digital computer. Hexadecimal is used instead of binary for two
reasons: 1. It it easier for humans to read than binary. 2. A single hexadecimal digit can
be represented in a nibble (4 bits).
Computer security - Answer-Computer security is the protection of computers from
unauthorised access and the protection of data from loss.
What are the disadvantages of serial data transmission? - Answer-data is transmitted at
a slower rate than parallel data transmission
What is a Bitmap? - Answer-A method of representing images where a picture is divided
up into a grid of pixels. Each pixel is stored as a number which represents its colour.
magnetic media - Answer-for example, external hard disk drives and magnetic tape
, What are the disadvantages of parallel data transmission? - Answer-the bits can
become skewed over long distances
What is colour depth? - Answer-The term used to describe the number of colours that
can be stored in a bitmap image. This is usually described as the number of bits set
aside for each pixel. For example 8 bit colour depth can store 256 different colours.
What are the advantages of parallel data transmission? - Answer-Faster method of data
transmission. Works very well over short distances
What is sample resolution? - Answer-The number of bits used to store each sound
sample in an audio file. The more bits that are used for each sample the higher the
sample resolution and the more like the original sound it will be when played back.
optical media - Answer-for example, CDs, DVDS and Blu-ray disks
What is synthesis? - Answer-The process of creating the sound from an audio file.
cloud storage - Answer-for example, smartphone manufacturers provide online backup
facilities so that phone data can be automatically backed up each day
What is an example of serial data transmission? - Answer-sending data from a
computer to a modem for transmission over a telephone line
Server - Answer-a computer which handles requests from other computers.
What is an example of parallel data transmission? - Answer-sending data to a printer
from a computer using a ribbon connector
What is sample frequency? - Answer-How many sound samples are taken per second.
This is measured in hertz (Hz). The higher the sample frequency the more samples are
taken per second and the more like the original sound it will be when played back.
Request - Answer-a communication which asks for data to be transferred.
What is USB an example of? - Answer-asynchronous serial data transmission
What is a compression? - Answer-A process that results in needing less storage space
(bytes) to store some data.
What is lossy compression? - Answer-A compression method that would make it
impossible to derive the original data. Common methods are the JPEG image format
and the MP3 audio format.
Physical security - Answer-security which prevents physical access to a computer.
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