unit 2.6 - computational thinking

unit 2.6 - computational thinking

1. (1) BIT - is a binary digit. A binary digit is the smallest unit of data a computer can store. Each bit is presented using either a 1 (true) or 0 (false).

2. (2) NIBBLE - it describes a group of 4 bits. A nibble is useful when converting between binary and hexadecimal. A nibble will only cover decimal numbers between 0 and 15.

3. (3) BYTE - is a collection of 8 bits. Keyboard characters take up 1 byte (8 bits) of storage. Every other storage is made up from multiple of bytes.

4. (4) KILOBYTE - 1 kilobyte = 1000 bytes. However because we are counting in binary it is actually 1024 bytes.

5. (5) MEGABYTE - 1 megabyte = 1000 kilobytes. We use megabytes to measure transmission speeds on the web and also storage space on a CD).

6. (6) GIGABYTE - 1 gigabyte = 1000 megabytes.

7. (7) TERABYTE - 1 terabyte = 1000 gigabytes. Hard disks are measured in terabytes.

8. (8) PETABYTE - 1 petabyte = 1000 terabytes.

9. Hexadecimal - use the base-16 number system .There are sixteen possibilities: 1,2,3,4,5,6,7,8,9,A,B,C,D,E,F

   • To convert hexadecimal to denary (base-10) - Base 16 is represented by the following place value - 256(16^2) , 16(16^1) , 1(16^0). Therefore to convert 4C from hexadecimal into base 10 : 64+12= 76
   • To convert denary to hexadecimal: EG: convert 167 into hexadecimal - divide the number by 16 =10A. Record the remainder = 7. Therefore the answer is A7.
   • Hexadecimals are used by computer scientists for the following reasons: - Binary produces long strings and can be difficult to work with. Hex is shorter. - Hex can be easily converted to/from binary as there is 1 hex digit per nibble. - Hex is less susceptible to error. - Technicians prefer hexadecimal as it's shorter and less digits to remember.
   • Binary - machine code

10. ASCII - american stand code for information interchange. It is used to allow the computer to understand the characters that have been typed in by a human. ASCII uses 7 bits. Whereas, extended ASCII uses 8 bits

11. Unicode - uses 2 bytes that give us 2^16 possibilities (65536). It allows a user from any country to select their language

12. Bitmap - The page is divided into an invisible grid and each pixel is assigned a colour. Bitmap requires more room needed and becomes blurred when expanded

13. Vector - Are based on mathematical formulas and can be scaled infinitely without any loss in quality. Every line and shape has a value that changes when the image expands. Vector requires less room and doesn't become blurred when expanded.

14. Metadata - The number of pixels we use is known as the RESOLUTION. Computer screens - 1366x768 pixels = 1049088 pixels.

15. Digital Audio - Sound exists as waves. The quality that the samples are stores with depends on different factors.

    • Sample frequency - The no. audio samples captured every second.
    • Sample size/ Bit depth - The no. bits available fro each sample
      • All three of these affect the quality of the audio.
    • Bit rate - The no. bits used per second of audio .

16. Data Compression - is the process of encoding data so that it needs fewer bits/bytes to represent it .

    • LOSSLESS COMPRESSION- can compress data files without losing any of the information. -are reversible so that the original data can be reconstructed. - not all the data files can be compressed using lossless compression
    • LOSSY COMPRESSION - can compress data files but does lose some of the information . - It's acceptable if some loss of accuracy is acceptable eg: video/audio
    • ADV: -can produce smaller data files.
      • DISADV: - No good if 100% accuracy required. eg:text files.