"Code" after reading notes--14th to 25th chapter

1. Feedback and Triggers

   The oscillator does not require human intervention to be able to independently and continuously achieve disconnection and closure. All computers rely on some kind of oscillator to make other parts work synchronously.

   When two switches are disconnected, the circuit has two stable states, such a circuit is called a trigger. Triggers are memory-capable of keeping information.

   Trigger:

   The circuits commonly used in the Code book

oscillator
divider
8-bit line wave (async) counter
8-1 selector
3-8 Decoder

2. Bytes and hexadecimal

   After reading this chapter, the individual thinks that the hexadecimal appearance should be to be simple and clear to represent the byte bar. The four-way representation is only 1 time times shorter than the binary, octal does not implement 8 bits of bytes, and 256 is too complex.

   In hexadecimal, a two-bit signed number is negative if it starts with 8, 9, A, B, C, D, E, or F.

4. Memory Organization

   RAM: Random access memory. Be aware of the conceptual differences between random and sequential storage.

   In general, when it comes to memory, how many bytes people default to. When it comes to transmitting data on a line, the number of bits is defaulted. As mentioned in the

   Book: Since 9 relays are required for each memory according to our design, the 64kx8 RAM array requires nearly 5 million relays. Are you in doubt here? Are the relays used in selectors and decoders not counted?

   Storage is organized like this:

    

6. Automatic operation

   is the so-called instruction code or opcode an element of the CPU instruction set?

   The most basic instruction code: Load,store,add,substrate,halt. Add with Carry,substrate with borrow. Jump,jump If XXX. Carry plus and borrow are used to carry a carry latch (1 bits).

   The carry input of the 8-bit adder is set to 1 when the subtraction operation is performed, or if the data output of the carrying latch is 1 and a carry addition or borrow subtraction instruction is performed. When the add operation is performed, the carry input is set to 0. When the borrow subtraction operation is performed and the data output of the carry latch is 0 o'clock, the low subtraction results in a borrow, so the accumulator needs to be 1 less, so the carry input is set to 0.

   The transfer instruction is equivalent to forcing the counter to change the value equal to the transfer address.

   0 Latch: Input all is 0 o'clock, 0 flag position is 1. The store directive does not affect the zero flag bit. The 0 flag bit can only be affected by addition, subtraction, carry addition, borrow subtraction directives, which are the same values set in the most recent execution of these directives.

   Controlling repetition or looping is the difference between a computer and a calculator.

   The processor has some components. One that has been identified is the accumulator, which is a simple latch that is used to store data inside the processor. The 8-bit counter and the 8-bit adder are called arithmetic logic units or ALU in the computer we are designing. The ALU can only perform arithmetic operations, mainly addition and subtraction. In complex computers, the ALU can also perform logical operations, such as "and", "or", "XOR". The 16-bit counter is called the program counter PC.

   It is best not to use real numeric addresses when writing code, as they will change. A better approach is to use labels to specify the storage units, which are simple words.

   There was an analog computer, but they were disappearing. I wonder if I will meet you later?

   The development process of adder:

7. From Abacus to Chip

   Turing first proposed the concept of "computational power" to analyze what a computer can and cannot do. The following talks about "artificial intelligence", called Turing Test.

   Turing Test: If the computer can answer a series of questions raised by the human test in 5 minutes, and more than 30% of the answers let the tester mistakenly think that the human answer, then the computer passed the test. But 30% is a projection of Turing's ability to think about machines in the 2000, and we are lagging far behind this prediction. June 7, 2014 is the 60 anniversary of the death of Alan Turing, the father of computer science, Alan. On this day, at the "2014 Turing Test" conference held by the Royal Society, the chat program "Yukin Gustmann" (Eugene Goostman) First "passed" the Turing test.

   Von Neumann architecture: The computer should use binary; the computer should have as large a memory as possible to store program code and data; Directives should be stored sequentially in memory and addressed by program counters, but should also allow for conditional transfers, a design thought called stored-program concepts. Von Neumann architecture of a computer takes a lot of time to fetch instructions, which is a bottleneck in the architecture of von Neumann.

   Two n-type semiconductor clip a P-type semiconductor can be made into an amplifier, called an NPN transistor, the corresponding three parts are collector (Collector), base (base) and emitter (Emitter).

   There are 2 popular families that make up the components of integrated circuits: TTL (Texas Instruments) and CMOS (National Semiconductor Corp.). But it was the first time that Intel had built a complete computer processor on a circuit board with an integrated Intel 4004.

   The construction of an oscillator requires only the use of quartz crystals, since quartz crystals have piezoelectric effects. With this feature, the quartz resonator can be used to replace the LC (coil and capacitor) resonant circuit, filter and so on.

   Piezoelectric effect: When the wafer is coupled with a change in the electric field, the Crystals produce mechanical deformations, and when mechanical forces are applied between the plates, the crystals produce alternating electric field, a phenomenon called piezoelectric effects. Using piezoelectric effect, when the plate is applied to alternating voltage, mechanical deformation is produced, and mechanical deformation in turn produces alternating electric field. Mechanical deformation amplitude is small, crystal vibration frequency is relatively stable. When the frequency of the applied alternating voltage is equal to the natural frequency of the crystal, the amplitude of the mechanical vibration increases sharply.

   There are three indicators that are often used to measure microprocessors: Data path bits, clock frequencies, and addressing capabilities. But they do not affect the ability of a single computer. In a sense, all digital computers are the same. If one processor's hardware can do no other processor, then other processors can be implemented with software. The fundamentally different processor is the speed!

   The development of the computer has a lot to do with Bell Labs, and Bell Labs was designed to make phone calls. After searching the internet, Bell Labs now belongs to Nokia. Gaped! And, of course, IBM is selling cards on its own. One of the transistor inventors, Shockley, left Bell Labs and went to California to start the first company, and then Silicon Valley.

   Summary of the history of computer development (via:http://blog.sina.com.cn/s/blog_7155b61b0100p8vj.html)

time	event	details
1833	Charles Babe (English) Design analytical machine (not manufactured in person).	Resolver was the closest computer invention of the 19th century. The design contains a storage system and an operator, the most essential part is the card can be programmed, and can carry out conditional transfer instructions. Babechi is hailed as a pioneer of modern computers.
1890	Herman Holleris (United States) design and manufacture business card making machine.	The invention of the machine is mainly for the convenience of a 10-year United States Census, and the inventor Holleris himself is the census of 1880 statisticians. The machine was a big success in the 1890 census, and in 1896 he set up a watchmaking company, which was renamed International Business Machine Company (IBM) in 1924.
1935	Conrad Zouze (Germany) designed and manufactured the first relay computer Z-1.	Zouze is a recognized father of electromechanical computers, and he was a engineering student when he was designing Z-1. The Z-1 is binary and can be programmed with film-based film. Zouze his inventions with a lifetime of improvement.
1943	Howard Aiken (US) design and manufacture of the first digital computer Harvard Mark I.	Howard Aiken was a graduate student at Harvard University, working with IBM to develop a computer because of the need for a method to perform a lot of repetitive calculations.
1943	Allen · M. Turing (English) and other people designed and manufactured vacuum tube computer Colossus.	Colossus is used to decipher the German code. The vacuum tube is easily burnt, but the maintenance is much less complex than the relay. Although the vacuum tube (microsecond) is 1000 times times faster than the relay (millisecond), the early computers are not very concerned with the computational speed problem because the speed bottleneck mainly focuses on the time of reading the program from the paper tape.
1945	Moore Electrical Engineering School design and manufacture vacuum tube computer ENIAC.	ENIAC uses 18,000 vacuum tubes, weighing 30 tons, is by far the largest computer.
1946	von Neumann (Hungary-born-American residency) presents a stored procedure concept.	Store Program concept: Store instruction order in storage and address it with program counters, but also allow conditional transfer. The stored-Program concept is a revolutionary idea that today is called the von Neumann architecture and is the foundation of modern computer design. But the von Neumann architecture also has the disadvantage that it takes a lot of time to get instructions from memory to the CPU to prepare for execution, which is called von Neumann bottleneck.
1948	Lloyd Shannon (Mei) put forward the concept of" bit "during Bell Labs and established the research field of" Information theory ".	Information theory involves the transmission of digital information in the presence of noise (which often hinders the transmission of information) and how information is compensated.
1947	William Shaokre (US), John Barton (Mei) and Watt Bratton (US) invented transistors at Bell Labs.	Transistor was the greatest invention of the 20th century, and the trio won the 1956 Nobel Prize in Physics. Semiconductor refers to its conductivity can be controlled by a variety of methods, it is germanium, silicon and other pure semiconductor doped impurities made. The principle of logic switch is the same as the relay, vacuum tube, but its response speed is nanosecond, and its service life is long enough.
1958	Robert Noyce (US) and Jack Kilby (United States) also invented integrated circuits.	ICs (also known as chips, ICS) rely on a method that can cause many transistors, resistors, and other electronic components on a single wafer.
1965	Gordon · E. Moore (US) discovers Moore's law.	Moore's law: every 18 months (1.5) The number of transistors that can be integrated into a chip doubles.
1971	Intel developed Intel4004, the first "computer on a Chip" (microprocessor).	Inter company by Robert Noyce and Gordon · E. Moore established. The former invented the integrated circuit, the latter found Moore's law. The Intel4004 lays out three main parameters of the microprocessor, namely data width, clock frequency and addressing range, and these three parameters roughly describe how fast the processor is running.

2. Two kinds of typical microprocessors

   In April 1974, Intel launched 8080; in August 1974, Motorola launched 6800.

4. ASCII code and character mapping

   Return the print head to the beginning to print the next line from the left side of the paper, which is the carriage return. Move the print head immediately to the next line of the line you just completed, which is a newline.

   BCD code: Also known as two-decimal codes. This encoding uses four bits to store a decimal digit, making the conversion between binary and decimal fast. The most commonly used in the design of the accounting system, relative to the general floating-point notation, the use of BCD code, both to preserve the accuracy of the value, but also to avoid the computer as a floating-point operation of the time spent. Common BCD Code has 8421BCD code, 2421BCD code, 3 yards remaining.

   The American Standard Code for Information Interchange, abbreviated as ASCII, is 7-bit encoded on "technology," but is generally stored in 1 bytes. Therefore there is an extended ASCII character set, the highest bit being 1.

   ANI A, DFh: Except for the 3rd digit from the left side is placed 0. Setting this bit to 0 also converts the lowercase letters of the ASCII code to uppercase. Very ingenious!

   According to the published ASCII code standard, 10 ASCII code codes (40h, 5Bh, 5Ch, 5Dh, 5Eh, 60h, 7Bh, 7Ch, 7Dh, and 7Eh) can be redefined and used for a country. In addition, if required, the number sign (#) can be replaced with the pound sign (￡), and the dollar sign ($) can be replaced with the universal currency symbol (¤).

   The ASCII code is a single-byte character set, representing a maximum of 256 characters. To represent more characters, a double-byte character set, with Unicode, can represent 65,536 characters. Unicode is also compatible with ASCII code.

   A discussion of Unicode and UTF-8: https://www.zhihu.com/question/23374078

   What are the main differences between the GB2312, GBK, GB18030 and other character sets? https://www.zhihu.com/question/19677619

6. Bus connection

8. Operating system

10. Fixed-point and floating-point numbers

12. High-level and low-level languages

14. Graphic Revolution

"Code" after reading notes--14th to 25th chapter