1. Processing Data

2. Representing Numbers  Recap on Binary Numbers  Binary digit (1 or 0) – known as a ‘bit’, short for BInary digiT – bits generally grouped together in 8-bit bytes – a byte can hold 2 8 combinations of 0s and 1s – This means that, for example, 256 different characters can be represented.  When ‘A’ is pressed, 01000001 is sent to the CPU.

3. Some of the ASCII codes Char ASCII CharASCII Char ASCII Char ASCII spac e 010000080111000P1010000h1101000 !010000190111001Q1010001i1101001 (0101000@1000000X1011000p1110000 )0101001A1000001Y1011001q1110001 *0101010B1000010Z1011010r1110010 +0101011C1000011[1011011s1110011,0101100 D 1000100\1011100t1110100 -0101101E1000101]1011101u1110101.0101110F1000110^1011110v1110110 /0101111G1000111_1011111w1110111 00110000H1001000'1100000x1111000 10110001I1001001a1100001y1111001 20110010J1001010b1100010z1111010 30110011K1001011c1100011{1111011 40110100L1001100d1100100|1111100 50110101M1001101e1100101}1111101 60110110N1001110f1100110~1111110 70110111O1001111g1100111del1111111

4. Real Numbers  Numbers with a decimal point are known as real numbers  The system for holding numbers in this way is not part of the course.  Be aware that if ‘numbers’ are to be used in calculations, they have to be held as numbers and not as text.

5. Digitised Sound  Sound can be input using a number of devices  As with basic telephone line, sound is analogue (wave form)  Convert to digital form (i.e. a binary pattern) for storage and processing  Hardware – sound card does conversion from analogue to digital and vice versa.  Sampling rate – how often the card takes a digital snapshot. (higher – more accurate) – Measured in kHz – CD requires 44kHz (samples per second  Resolution – accuracy of measurement of amplitude of sound. 8-bit board gives 256 (2 8 ) sound levels. 16-bit board gives 65,536 (2 16 ) levels of amplitude.  Sound card has built-in synthesiser.

6. Musical Instrument Digital Interface  MIDI is industry standard applied to: – Electronic musical instruments – Hardware, cables, connectors & data  MIDI interface allows computer to communicate: – Keyboards, drum pads, guitars etc.  MIDI data system stores all info. Necessary to synthesise musical sounds.  Digitally stored data is very compact: – 30k for (1 minute of music) – Compared with 600k recorded  MIDI files on CDs or diskettes can be loaded and re-played through sound card. Music can be altered because it is stored as instructions.

7. Bit-Mapped Graphics  Screen is divided into a grid – Each square is called a pixel (picture element)  Higher Resolution has more squares – Standard used to be 640x480, is now 800x600 but rapidly moving toward 1024x768 as standard – Monochrome only requires 1 bit in memory, (if 1, the pixel is on, if 0 the pixel is off). – For colour, each pixel requires 1 byte in memory, giving up to 256 colours for each pixel. – Memory is on graphics card – so RAM is not used.  The higher the resolution, the sharper the image

8. Bitmapped and Vector-based Graphics  Bitmapped images –are collections of pixels –Images created by setting colour and other attributes for each pixel –the amount of memory required is dependent upon the display adapter –Problems: May not look correct if transferred to another machine with different adapter or resolution Distortion occurs when you try to enlarge the image

9. Bitmapped and Vector-based Graphics  Vector-based (or object-oriented) Graphics – Image is based on geometric data NOT graphic data – A line defined by is endpoints, length, colour and so on Used by CAD programs (or special graphics software) to create the line on any screen regardless of its resolution Thus, line-art of this type said to be device- independent Can be re-sized without any distortion – Allows for much greater accuracy