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Joel Alvarez Myrrie
Chapter 1
Brief summarize
General knowledge
* Inside today’s computer information is encoded in patterns of 1’s and 0’s. They are called bits.
* They are only symbols whose meaning relies on the application at hand.
* Boolean operations: True/false values.
* Gates: A device that produces the output of the Boolean operation when given the operation’sinput values.
* Flip-Flop: It’s a circuit that produces an output value of 0 or 1.
* Stream: String of bits, which are very difficult for human to understand so we use a shorthand notation called hexadecimal notation.
* In particular, hexadecimal notation uses a single symbol to represent a pattern of four bits.
Storing data
Mainmemory
* For the purpose of storing data, the computer contains a large collection of circuit (such flip-flops) each capable of storing a single bit. This bit reservoir is known as the machine’s main memory.
* That main memory is organized in manageable units called cells (cell size being 8 bits, known better as byte).
* 0 1 1 1 1 1 1 0 Less significant bit.

Mostsignificant bit.
* Each cell is assigned a unique name, called its address (like identifying houses in a city by their numbers).
* Main memory is often called RAM.
* 1 KB equals to 1024 bits.


Mass storage

* Due to the volatility and limited size of computer’s main memory, most computers have additional memory devices calledmass storage.
Magnetic devices
* Thin spinning disk with magnetic coating is used to stored data.
* Each track is divided into small arcs called sectors on which information is recorded as continuous strings of bits.

Optical systems
* Another class of mass storage applies optical technology.
* Example: CD
* Information is recorded on them by creatingvariations in their reflective surfaces.
* 2KB equals to 1/75 of a second of music in the case of audio recordings.

Flash drivers
* Flash memory has alleviated the drawback of magnetic or optical technology which consist of the slowness (electronic circuitry is faster).
* Because of high capacity and the easiness ofconnecting or disconnecting from computers, they are good for off-line data storage.
* They don’t require physical motion so they have shorter response times and don’t suffer from physical wear.
* Buffer: It’s a data storage area use to hold data on a temporary basis.

Representing information as bit patterns.
* ASCCI: Uses patterns of 7 bits to represent the upper and lowercase letters ofEnglish alphabet, punctuation symbols, the digits 0 through 9 and so on. Latter they added one bit making it 8 bits.
* Unicode was developed because in so many Asians alphabets the bits to represent their alphabet letters were insufficient so they created Unicode with a unique pattern of 16 bits to represent each symbol.
* A file consisting of a long sequence of symbols encoded using ASCCIor Unicode is called text file.
* Text files contain only a character-by-character encoding of the text whereas files from word processors contain numerous proprietary codes representing changes in fonts, colors and so forth.

Representing images
* One means of representing images is to interpret the image as a collection of dots, each of which is called a pixel. Such a collection iscalled bit map.

Storing notations

Two’s complement
* O is positive and 1 is negative
* Copy the bits from right to left (as they are represented) until a wild 1 has been copied.
* Then, complement the remaining bits.
* -17 11101111 ya que 17 00010001 (two’s complemet)
* Addition:
7 0111 0111
-5 -0101 +1011...