Cambridge IGCSE Computer Science
Paper 1
denary number - Answer- a base 10 number in which each digit is worth 10 times the digit to its right, and digits can have
10 values : 0 to 9
right, 16 - Answer- hexadecimal number
a base 16 number in which each digit is worth 16 times the digit to its ____________, and digits can have _____ values : 0
to f
4 - Answer- The number of bits needed to store a hexadecimal digit
bit - Answer- a single true/false value (short for binary digit)
debug - Answer- to find errors in software
digital - Answer- any quantity that has a precise, discrete value that can be represented as a number (but cannot assume
a continuous range of values)
byte - Answer- a group of 8 bits
nibble - Answer- a group of 4 bits (half a byte, equivalent to one hex digit)
kilobyte - Answer- 1024 bytes = 2^10 bytes
megabyte - Answer- 1024 kilobytes (2^20 or roughly 1 million bytes)
gigabyte - Answer- 1024 megabytes
a,b,c,d,e,f - Answer- digits in hexadecimal that are equivalent to 10,11,12,13,14,15
colour, addresses, machine, memory - Answer- *uses of hexadecimal numbers*
___________codes in HTML
-Media Access Control (MAC) and IP _____________
-assembly language and ____________ code
_____________ dumps
-specifying memory locations
memory dump - Answer- An output of memory contents onto the printer or screen.
Usually represented in hexadecimal.
mark-up language - Answer- a language used when processing and presenting text, e.g. HTML.
NOT a programming language but contains information on how text should be structured and presented (e.g. paragraphs,
colour, font, underlining etc.) and can also be used to embed images, hyperlinks etc.
unique, hardware, 48, manufacturer, serial - Answer- MAC address
A _______________ identifier number that identifies a device on a local area network (LAN).
The address is typically *static* and set in the ____________ by the manufacturer.
The name is an acronym from *media access control*
STRUCTURE:
-consists of _____ bits displayed as pairs of hexadecimal.
-The first part is the ____________________ ID, the second part is the ____________ number
digit, parity, repeat - Answer- *Methods of data verification*
,for short numbers (e.g. credit cards, ISBNs):
-check ____________
for transmission of more data, over a network:
-______________ bit/checks
-checksum
-Automatic _____________ reQuests (ARQ)
repeat reQuest., notification, received, re-sent - Answer- Automatic ________________ _____________ (ARQ)
A method of data transmission employing an error-detecting code so that any error detected by the receiver initiates a
repetition of transmission of the incorrectly received message.
The sender also requests a _______________ that the data has been ________________ correctly.
If no delivery notification is received the message is ____________ periodically until either it has been safely delivered or a
time-out is reached.
Instructions, digital musical instruments, synthesizer - Answer- *MIDI (Musical Instrument Digital Interface)*
A set of standards / file format used to represent music in digital form. Used for recording / generating synthesizers and
other digital instruments
MIDI files
• contain _________________ of how to make sound
• Non-audio recording
• File created using ____________ ____________ ________________
• Produced by ____________________
• Used when composing music
• Individual notes/instruments can be changed
sampling rate, sampling resolution, lossy, repeated, indexing - Answer- *Sound Sampling*
The _____________ ____________ is the number of times per second the sound wave (i.e. pressure, or the analogue
signal from microphone) is sampled
The ____________ ____________ is the number of discrete levels that the analogue signal is converted to.
The analogue signal from the microphone must be converted to digital by ADC.
To compress the file by __________ compression, both of these can be reduced.
To compress with lossless compression we could use run-length or Huffman encoding. (i.e. build a table of ____________
values and represent the data by ___________ into that table
WAV - Answer- (Waveform Audio File Format) an audio coding format standard for storing an audio bitstream of
*uncompressed* audio data.
This is a high quality audio file format used for professional music / broadcasting and needs very large file sizes
MP3 - Answer- A standard format for music files sent over the Internet that compresses music.
not as high quality as WAV but has much smaller file sizes.
commonly used in personal music players / ipods.
• Digital recording of sound (samples/resolution)
• Produced by recording software / microphone
• Used when distributing sound files
• Compressed file format (lossy)
JPEG - Answer- The most common graphic file format, full colour graphic format (16.7 million colors) with a relatively
small file size
a standard image format for containing compressed image data. This results in good reduction in file size and maintains
reasonable image quality. Commonly used by digital cameras, phones.
the compression is lossy
, MP4 - Answer- mpeg 4; a compressed file format that can be used for audio or video; appropriate for streaming
the compression is lossy
compression algorithm, can, repeated, dictionary - Answer- *lossless compression*
a data compression algorithm that allows the original data to be perfectly reconstructed from the compressed data.
A _______________ _________________ is used
No data is lost in the compression process. The original data _____ be recovered
for string/text messages:
________________ words / patterns are identified and are *indexed*/put into a table.
-words are replaced with their *index*. their positions and the number of times the word/pattern appears is stored in the
table.
for images:
-A ________________ of pixels is created
-The number of times a pixel is repeated in a row is stored and represented by run-length encoding
for sound:
repeating sampling levels are put in a dictionary and the signal is represented by run-length encoding
compression algorithm, cannot - Answer- Lossy Compression
data compression where there is some loss of information or reduction in quality : the resulting files are smaller but
A __________________ __________________ is used
Some data is lost.- the original data _______________ be reconstituted.
Images/video:
reduce the colour depth and pixel resolution
Sound:
reduce the sampling frequency and sampling resolution
RAM (Random Access Memory) - Answer- a form of fast volatile primary memory which can be accessed directly by the
CPU
It holds the operating system and the data and instructions currently being used.
persistent - Answer- describes memory which retains information even if the power supply is interrupted. The opposite of
volatile.
Register - Answer- a small area of memory (e.g. 8 bits or 32 bits) within the CPU that stores values that are ready to be
processed by the CPU.
These can be general-purpose or special-purpose
Special purpose include: MAR, MDR, CIR, PC, ACC.
extension - Answer- the three-letter ending of a file name the identifies the file format (e..g. .txt identifies a text file, exe
identifies an executable (which can be "run" as a program by the operating system)
ASCII - Answer- a code for representing keyboard characters as numbers.
Has 7 bits = 128 characters
Short for American Standard Code for Information Interchange.
Unicode - Answer- an international extended code for characters which can represent characters from many alphabets
and languages.
Each character has 32 bits which gives 2^32 possible characters but only around 140,000 have an agreed definition.
