1 Data Representation Flashcards
convert binary to denary
right to left: each bit is worth 2 times the last bit, add up all the bits with 1’s
convert denary to binary
continually divide denary number by 2 until you get to 0, and put 1 as the remainder for odd numbers. To get the binary number, read the remainders from bottom to top
convert binary to octal (and vice versa)
for every 3 bits, right to left: each bit is worth 2 times the last bit, add up all the bits with 1’s, for 3 bits is one bit for octal
convert binary to hexadecimal (and vice versa)
for every 4 bits, right to left: each bit is worth 2 times the last bit, add up all the bits with 1’s, for 4 bits is one bit for hexadecimal
What is hex ABC in octal
ABC=5274
A=1010 B=1011 C=1100 ABC=1010 1011 1100 = 5274
5=101 2=010 7=111 4=100
Uses of the hexadecimal system (4)
error codes
MAC (media access control) addresses
IPv6 addresses
HTML colour codes
overflow error definition
the result of an equation exceeded the largest possible number which can be stored using a certain number of bits
logical shift definition
a logical shift moves binary numbers to the left or the the right. Each shift left is equivalent to multiplying the binary number by 2 and each shift to the right is equivalent to dividing the binary number by 2
what is two’s complement
allows binary representation of negative integers
the most important bit (on the far left) of the number becomes a negative
there must be a one in the MIB
what is an ASCII code system
American Standard Code for Information Interchange
a character set that consists of 7-bit codes (0-127 in denary)
represents the letters, numbers and characters found on a standard keyboard, together with 32 controd codes
sound sampling meaning
measuring the amplitude of the sound wave
sampling rate meaning
the number of samples taken in 1 second or the frequency of sound samples taken
measured in hertz (Hz)
sampling resolution meaning
the number of bits per sample
also known as the bit depth
pixels meaning
the smallest element of a bitmap image
colour depth meaning
the number of bits used to represent each colour for each pixel
image resolution meaning
the number of pixels that make up an image
for example an image could contain 4096 x 3072
bit meaning
the basic unit of all computing memory storage terms
the word comes from (B)inary dig(IT)
the smallest unit of memory in a computer
what is one byte in bits
8 bits
order of memory size in denary system
1 bit
1 Byte
1 kilobyte
1 megabyte
1 gigabyte
1 terabyte
1 petabyte
1 exabyte
order of memory size in binary system
1 bit
1 Byte
1 kibibyte
1 mebibyte
1 gibibyte
1 tebibyte
1 pebibyte
1 exbibyte
file size of an image formula
file size = image resolution (in pixels) x colour depth (in bits)
file size of a mono sound file formula
file size = sample rate (in Hz) x sample resolution (in bits) x length of sample (in seconds)
bandwidth meaning
the maximum rate of transfer of data across a network
reasons to reduce/compress files
to save storage space on hard disk drives/solid state drive
to reduce the time taken to stream a music or video file
to reduce the time taken to upload, download or transfer a file across a network (reduces bandwidth)
to reduce costs. for example, when using cloud storage, the cost is based on the size of the files stored
what is lossy file compression
the file compression algorithm eliminates unnecessary data from the file
this means the original file cannot be reconstructed once it has been compressed
results in some loss of detail when compared to the original file
what might lossy file compression do to an image
reduce the resolution
reduce the colour depth
what might lossy file compression do to a sound file
reduce the sampling rate
reduce the resolution
removal of sounds outside the human ear range
if two sounds are played at the same time, only the louder one can be heard by the ear, so the softer sound is eliminated. this is called perceptual music shaping
examples of lossy file compression algorithms
MPEG-3 (MP3)
MPEG-4 (MP4)
JPEG
what is lossless file compression
with this technique, all the data from the original uncompressed file can be reconstructed
none of the original detail from the file is lost
what is RLE
run length encoding
it is a form of lossless/reversible file compression
reduces the size of a string of adjacent, identical data
a repeated string is encoded into two values:
-the first value represents the number of identical data items in the run
-the second value represents the code of the data item