ASCII and Unicode Flashcards
Explain why binary codes are used to represent characters, numbers and symbols.
Because this is what the computer understands, and otherwise we would not be able to input letters. These letters are much easier to type than binary codes.
Explain why the 7 bit standard ASCII code needs to have the highest (first) bit set to 0
Because in the English language, we have very few special symbols (such as an umlaut). Other languages use these more.
Giving an example, show how a letter in the English alphabet is stored using ASCII
The number is converted into binary (a = 01100001) and then displays the letter on the screen. This is then stored in this 8-bit binary code system which the computer can understand.
How many possible combinations are there in the 8-bit character system?
256; 2^8 as there are 8 possibilities of 1 or 0.
How much storage does 1 letter take up?
1 byte
Explain the difference between standard ASCII and extended ASCII.
ASCII is the simple letters and punctuation of the English Language. Extended ASCII uses symbols from other languages like German and Irish (like accents and umlauts). Normal ASCII uses only 7/8 bits, whereas Extended ASCII uses 8/8 bits.
Explain how the computer recognises which letter has been requested via the keyboard.
When a keyboard key is pressed, a message is sent to the BIOS which then converts it into binary code to store in the computer. For example a is pressed, and the Operating system or BIOS reads one byte. The letter is now converted into binary (a = 01100001).
Explain the difference between a character set and font style.
Font files contain the bitmap image information for the display of characters. Character sets are groups of certain characters, usually varying by country (e.g. German character sets would have umlauts in them).
Explain the difference between Unicode and ASCII.
ASCII uses a 1 byte system, which is great for most common languages (like English, French and German) but for more complex languages, like Chinese and Japanese, we want all our languages to be in the same place. So we use Unicode, which uses a 2 byte system, which gives us so many more combinations for all the different symbols in the world’s language systems. (2^16 instead of 2^8)
