The No. 01 lesson in C language learning: Talk about computers first.

Dear classmates, I will be your teaching assistant for the new semester. My personal information, your classroom teachers have already introduced, so I will not be wordy here. Next, let's talk about today's topic: "First to talk about computers."

Presumably see this topic, you all must be not willing to click in, after all, now you are, must be almost every day to face the computer (to know, now your mobile phones, are more advanced than the earlier computer, the performance is much stronger). But don't know if you've ever thought about some of the problems associated with it. Like what:

1. How it enters the operating system after pressing the switch button;
2. After entering the operating system, how does it start the first program;
3. Software is how to control the hardware (such as you use a mobile phone to take a picture, it is how to open the camera, how to collect a picture, how to display on the screen of the phone)
4. ......

After you ask these questions, you will feel, "yes" This is why, the inside of the computer, have experienced something, realized the various functions listed above.

These problems can be kept in your later study slowly a little bit of the untie, such as computer principles can tell you how the computer in the end how to enter the system, it is how to control the computer hardware. However, before learning these courses, C must be a must-have skill, and even you need to have a little compilation of the basics. Here, let's simply talk about C language.

Talk about C language must talk about the computer.

computers: Hardware and software Computer software

The computer itself is an electronic device capable of calculating and logically judging. The so-called calculation, that is, it can be entered after you input "2", the so-called logical judgment is that you enter "Today Rains Rain" gives "under" or "no" assertion. Of course, this is just a simple explanation, the computational and logical judgment of computer processing may be more complex shuffling than the example above. Here, we can call the input "+" or "rain is not raining Today" as " data ", it is the calculation of these data or judgment, is an operation, the final presentation. Therefore, the function of the computer can be summarized as the input data processing, and then output.

Generally speaking, if only the real entity of the computer, it is impossible to complete the process of data processing, because the data processing is often predetermined by the person. The pre-set process, we can call it programming. The result of the preset, we can call it a program.

Computer hardware

In general, no matter how the shape of a computer changes, it is usually composed of 6 parts:

1. Input unit: Used to receive data, paddle, if there is no data, the computer does not know what to do good;
2. Output unit: Used to process the output of good data, the data is very hard to handle, always show up to see;
3. Memory unit: Data coming and going, always have a temporary inn;
4. Arithmetic logic unit (arithmetic and logic Unit,alu): Used to perform subtraction these mathematical operations;
5. CPU (central processing UNIT,CPU): Used to coordinate the affairs of each unit;
6. Secondary storage unit (secondary storage unit): Used to store some data that needs to be saved for a long time.

(in some traditional computer textbooks, there are only 5 logical units, there is no sixth secondary storage unit.) or using the concept of storage, collectively, the third and sixth)

Machine language, assembly language and high-level languages

However, the computer itself is not able to understand the human language, because his internal use of electric drives of various electronic devices, they can only feel the power (remember when a child with the tongue licking the battery, electricity is salty, no electricity, no taste). So a computer can understand just a bunch of signs that have electricity and no electricity and no electricity.

Machine language is a little bit too good to understand, so smart humans will be a bunch of fixed "power off" into the code called "Assembly", and then use a program, the assembly code as a data input, output a bunch of "electric power" machine code. However, if you have read assembly language you will find that the assembly itself is not so well understood. Laziness is the first impetus for the development of science and technology, and humans have invented a modern high-level language (language) in order to play with machines better.

A brief history of C language development

(So lazy, I will not write, please see here http://www.zhihu.com/question/22826568/answer/65915408)

The No. 01 lesson in C language learning: Talk about computers first.