Dark Horse Programmer---C basic 6 "#include指令" "Modular Programming" "Computer-based" "native code, inverse code, complement" "Bitwise operator"

Source: Internet
Author: User
Tags bitwise operators

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1. The file contains the format of the command:

1) #include "" Double quotation marks are files that contain the user's own written definition (which can be a header file or an ordinary file) #include是预处理指令, not a statement, no seal number required

2) #include <> header file containing a system (compiler comes with)

2, the document contains the essence:

Inserts the specified file contents into the command line position instead of the command line,

Include is not necessarily written on the first line;

3. Include File search order:

Replace the contents of the A.txt file in the current directory with the current write include;

Current directory: and Main. c a directory under the same folder;

#include "" The user's own

1) Look under the path where the current file is located;

2) If not found above, to the compiler include path lookup;

3) If the compiler include path is not found, the system's include path to find;

4) If the above three are not found on the error;

#include <> header file containing a system (compiler comes with)

1) Search under the include path of the compiler;

2) If you do not go to the system include path to find;

3) If there is no error;

"Modular Programming"

1. Modular Programming Concept:

The so-called modular programming (multi-file development), is the multi-file (. c file) programming, one. C File one. H file can be called a module;

The functions similar functions are encapsulated in different files;

2. Header files are used in the following scenarios:

1) through the header file to call the library function;

In many cases, the source code inconvenience to the user to publish;

2) Multi-file compilation

A slightly larger project is divided into several file implementations;

3) header file to enhance type of security check

3. Realize:

. C C Language source files:

. h (header) header file

1) method declaration but unable to implement method

2) Declaring a variable cannot define a variable

3) Declare the structure body;

4. Benefits:

1) time is only included. h file, external hidden source file

2) Division of the team

3) The function can be subdivided into several modules

5, multi-file development implementation (Modular development Implementation):


Implementation calculator:

1) Calculation link

2) Display Results

"The computer's binary"

1, the concept of binary:

is a way of counting, the representation of a numerical value;

2, common in the system:

Decimal, binary, octal, hexadecimal;

3, the binary digital Carry method:

Decimal: every ten into one;

Binary: 0.1 every two in one,

Writing form: Need to start with 0b,0b, 0b101

Octal: every eight in one, starting with 0, 045

Hex: Every 16 into one, 9,a,b,c,d,e,f, to 0x,0x beginning, 0x45;

4. Elements of the binary conversion:

1) Digits

A digit is the position of a digital in a number;



5. Conversion

10 binary Conversion 2 binary,

In addition to the second, decimal by 2 rounding method, high 0, the remainder of the reverse is the binary

2 Binary Conversion 10 binary

The right to add a bit,

2 binary Conversion 16 binary:

Integer part from right to left four bits and one, fractional part from left to right four bits and one; 4 in 1;

16 Binary Conversion 2 binary:

Convert 16 binary constants to 2, each split into 4 for bits, not enough for 0

"Original code, anti-code, complement"

1. Concept:

The method of storing data in a computer is in the form of complement and storage;

The data is divided into signed number, and unsigned number;

The maximum number of positive digits is 0, the highest negative number is 1;

For positive numbers: anti-code = = Complement = = Original Code

For negative numbers: anti-code = = Except for the sign bit, you take the reverse. complement = anti-code +1

2, the original code:

The original code is the absolute value of the symbolic bit plus the truth "+1" source =0000 0001 "1" Source =1000 0001

The range of values for 8-bit binary numbers is:

1111 1111, 0111 1111; positive 127 to negative 128

3, anti-code:

Positive inverse code is itself, negative anti-code is the sign bit unchanged, the rest of you take the reverse

4. Complement :

Positive complement is itself, negative numbers are added 1 on the basis of anti-code;

[+1] source =0000 0001 = 0000 0001 complement

[-1] source =1000 0001 = 1111 1110 anti = 1111 1111 complement;

5, why to introduce anti-code

Computer recognition symbol bit, subtraction is added a negative number, the computer can not do subtraction, the original code to calculate the negative 0;

"Bitwise operator"

1, bitwise operators

A binary calculation; applied only to an integral type.

1) & Bitwise AND: 9&4=0, with 1 The result is 1, 0 result is 0; any cardinality and 1 are 1; even and 1 are 0;

2) | The bitwise OR 1 is 1, the same 0 is 0;

3) ~ 1 0,0 change to 1;

4) ^ Bitwise XOR or Same as 0, different 1

5) >> Right shift each binary all right shift n bit, low drop, high 0, equivalent to the original number/2^n;

6) << left displacement of each binary all left n bits, high drop, low 0, moving to the left N-bit, equivalent to the original number *2^n; may change the positive and negative of a number;

2, Practical:

Any cardinality and 1 and both are 1; even and 1 are 0;

can use left and right to move again &1 the method to carry on 10 to convert 2 to enter the system;

1 int a=3, b=4; 3 //     a=a-b; 5 //     b=b+a; 7 //     a=b-a; 9     a=a^B;  One     b=a^B;  -     A=a^b;   

Two number Exchange

Dark Horse Programmer---C basic 6 "#include指令" "Modular Programming" "Computer-based" "native code, inverse code, complement" "Bitwise operator"

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