Data Flashcards
What numbers are used in the binary system and what states do they represent?
1 (on) and 0 (off)
In the denary system the place value increases by powers of 10. What powers do the binary place values increase by?
Powers of 2
What are binary codes used to represent?
Data and program instructions. Coded program instructions that are written by a programmer in a programming language ( eg: python) are converted into binary by a translator so that the computer can understand and execute them.
How does a computer tell the difference between a set of data and a set of program instructions?
There are different encoding formats for videos, audio, images and character sets. This means that the computer knows what it is storing. (Look at this on BBC bitesize.)
How many bits are in a byte?
8
What are the place values that are used to represent a byte of data?
1, 2, 4, 8, 16, 32, 64 and 128.
What is a nibble of data?
Half a byte (4 bits)
How do you convert a number from binary to denary?
Add together all the place values of the columns with a 1 in.
How do you convert a positive number to its negative equivalent in two’s compliment?
Flip all the bits except the smallest one. Eg: 0011 becomes 1101 in two’s compliment.
What are the two methods of representing negative numbers? Describe them.
In two’s compliment the most significant bit (the bit that is furthest to the left) becomes negative. Eg: in a nibble of data 8 becomes -8. In sign and magnitude the most significant bit column becomes a + or - sign. A 1 in that column means that the number is negative and a 0 means that the number is positive.
What are the problems with sign and magnitude?
There are two ways to represent zero. ( 11111111 and 10000000)
The range of values that it can represent is smaller than two’s compliment.
Addition doesn’t always work.
How are binary numbers converted into hexadecimal?
Split the binary number in half then use the place values to convert each half into denary. Convert each denary number into a hexadecimal value.
How are hexadecimal numbers converted into binary?
Each hexadecimal value is converted into denary. Each denary number is converted into a nibble. The nibbles are combined to give the binary number.
Why is hexadecimal used?
It is easier for humans to use hexadecimal instead of long strings of binary digits.
What is lossy compression and what is it used for?
It reduces file sizes by deleting some data. The file has been irreversibly changed so the original file cannot be restored. In audio files very small differences in tone, frequency and volume are removed. In image files algorithms find areas where there are only slight differences. These areas are given the same value and the file is rewritten using fewer bits. Lossy compression is used for MP3 audio files and JPG image files.
