Computing technologies used in document processing

Nowadays, computer becomes our indispensible tool because we use it to create, store and access documents. We transfer messages, share feeling and communicate with others through documents. Due to increase efficiency, computing technologies used in document processing are highlighted. Documents are not confined to text document but also graphics and audio. This survey would focus on some basic computing technologies used in processing different documents.

First, ASCII is worth to mention here when talking about text document processing because it is the foundation stone of developing other coding schemes. ASCII stands for American Standard Code for Information Interchange. It is the most used coding system to represent data. Since computers are digital devices, they can have only two states, on and off. Our computers are digital so they can use two digits, 0 and 1 to represent these states. (Cashman, Shelly and Vermaat, 2008) However, 0 and 1, which are called bits, are not enough to represent all the alphabets, digits or symbols. Therefore, each ASCII code is stored using 7 bits and the standard ASCII can encode total 2^7 =128 characters.

Here is the standard ASCII table (CSGNetwork, 2009).

Table 1: standard ASCII table

The ASCII codes 0 – 31 are known as control characters, which are used to control peripheral devices like printers and is unprintable. The printable characters, ASCII codes 32-127, mean letters, numbers, punctuation marks or symbols.

As mentioned before, the standard ASCII can only represent 128 characters. There are several larger character sets that use 8 bits or 1 byte, which extend ASCII codes to 256 characters. The additional characters are used to represent the non-English characters, graphics character and mathematical symbols.

With the ASCII, we can make and store a text document.

For processing an image, I would like to talk about computing technologies used in capturing image with a digital camera. Digital camera uses digital sensor to record and digitalize the light rays from outside and store into a memory card. Its digital sensor (Cambridge in Colour, 2009) is composed of color filter and a sensor underneath it. Each color filter allows only one particular color to pass through. When the incoming light arrive the sensor array, the photons of the particular light ray will be collected. The relative quantity of photons is then sorted into various intensity levels.

Figure 2: typical digital camera’s sensor

Figure 3: color filter

That penetrated color is then digitalized by a 8-bit coding system. With the three primary colors which are red, green and blue, the total bits per pixel in a digital image should be 24bits. Each color would make up of 2^8 or 256 different combination and all three primary colors allows for as many as 2^(8*3) or 16,777,216 different colors at each pixel.

Therefore, the color at any point is conversed to numbers from 0-255 as a RGB form, for example: (0, 0, 0) is a black spot. With millions on little dot of pixel on the sensor, with the stronger processor to process the algorithm, we see a images just like we see it from film. Every pixel is converted into RGB code as mention, and it will be stored into memory card. This is why digital camera can capture the image and stored digital image in memory card.

Also, from the figures above, we can know that there are double numbers of green sensors than the others. It is because our eyes are more sensitive to the green color. This is how the digital cameras work.

The last point I want to mention is about sound record. To record sound, an input device such as microphone is needed. Sound is captured when the sound waves vibrate the membrane of the microphone. If we just graph the intensity and vibration of the membrane, we can obtain a smooth waveform curve showing the frequency of sound, like the following graph. Analog signal of sound is a continuous signal, representing the changes in physical properties of sound through time. As with most physical properties such as air pressure or temperature, the waveform of analog signals is more complex because different frequencies will be captured at the same time.

Graph 4: simple waveform curve of sound

Graph 5: digital approximation of Graph 4

When we record sound in a computer (LeLoup & Ponterio, 2010), the analog signals is represented by a digital approximation which is a series of binary number measuring the analog curve through an analog-to-digital converter. These numbers will then be stored onto recording media. Since it is not available for computer which has limited space to store the complicated analog curve, these binary numbers stored in computer just approximate the original analog signals. Just like the graph 5, the digital waveform can never be completely smooth. When we play the sound or music stored in computer, the sequence of those binary numbers transform back to the analog signals by a digital-to-analog converter. The signals are then amplified and transmitted to the loudspeakers.

In conclusion, computing technologies used in document processing help us a lot and they enrich our life. On the other hand, although the digital format media approaches the quality of traditional media, it would never be the same, as sampling and approximation took place during the transformation between the two. We cannot totally rely on the virtual world but appreciate and admire the real world.

References

1. Cambridge in Colour. (2009). Digital Camera Sensors. Retrieved October 2010, from Cambridge in Colour: http://www.cambridgeincolour.com/tutorials/camera-sensors.htm
2. Cashman, T. J., Shelly, G. B. & Vermaat, M. E. (2008). Discovering computers 2008: Complete. Boston, MA: Thomson course technology.
3. CSGNetwork.com. (2009). ASCII Character Set. Retrieved October 2010, from CSGNetwork.com: http://www.csgnetwork.com/asciiset.html
4. LeLoup, J., & Ponterio, B. (2010). Digital Sound Recording. Retrieved October 2010, from http://www.cortland.edu/flteach/mm-course/sound.html