Introduction to C Language Program first lesson/4

1. Program Notes

Note of the program: is the explanation of the program, to help people who read the code quickly understand the code, easy to work together.

Write program annotations A habit that programmers need to develop.

Issues you should be aware of when writing program annotations:

Comments generally include: ' File name, author, writing time, purpose, remarks '.

General: Important modules are also commented.

2. Memory, CPU, hard disk

Memory: Also known as flash, transient storage.

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/74/F6/wKioL1YvkWniX7ZIAADFqR8Euc4132.jpg "title=" memory. png "alt=" Wkiol1yvkwnix7ziaadfqr8euc4132.jpg "/>

CPU: Data processing, also belongs to the temporary storage.

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M01/74/F9/wKiom1YvkUuSc1lkAADP_h495Fs194.jpg "title=" Cpu.png "alt=" Wkiom1yvkuusc1lkaadp_h495fs194.jpg "/>

Hard disk: belongs to persistent storage.

650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M01/74/F6/wKioL1YvkZLRzbpiAADN70cv7V0210.jpg "title=" hard disk. png "alt=" Wkiol1yvkzlrzbpiaadn70cv7v0210.jpg "/>

3. Computer hardware (the most original computer)-operating system (to complete the interaction between hardware and users)-application software (applications running in the operating system environment)

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/74/F9/wKiom1YvkXny8HHXAAHwYcvrJTw381.jpg "title=" Operating system. PNG "alt=" wkiom1yvkxny8hhxaahwycvrjtw381.jpg "/>

4.ASCII (America Standard Code for Information Interchange: U.S. Standards for Information interchange codes.

ASCII Code table:

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/74/F6/wKioL1Yvkcrj9L4GAAR0J9Q-DZE273.jpg "title=" ASCII code table. png "alt=" wkiol1yvkcrj9l4gaar0j9q-dze273.jpg "/>

Special characters:

\ nthe line break

\ t transverse jump lattice

\ r Enter

\b Backspace

\ \ counter Slash

Print output: "0A"

printf ("%c", 48); //48 is the ASCII code for "0", where%c represents the output character.

printf ("%c", 65); //65 is the ASCII code for "A", where%c represents the output character.

printf ("%c", 0); //Decide whether to output English characters, mainly "%c" in effect.

printf ("%c", c);

Print output: 48 and 652 digits;

printf ("%d", 48); //%d of which represents the output integer number.

printf ("%d", 65); //6 where%d represents the output integer number.

printf ("%c", 0); //Decide whether to output English characters, mainly "%d" is in effect.

printf ("%c", c);

5. Constants, variables, data types

Constants: The amount of values that can not be changed during a program run.

Variable: The amount of value that can be changed during a program run.

The definition of a variable:

Format: Type + variable name

Naming rules:

Can only be made up of numbers, letters, underscores.

Numbers do not begin.

Can not drink the same keyword, such as: int void return, etc.

Variable names in the C language are case-sensitive.

For example, define variables:

int a = 3; meaning: The variable value 3 is stored in the variable name ' a ' and then stored in the storage unit with the variable address (number).

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/74/F6/wKioL1YvkiqzhhwJAAF5cF1mKJg632.jpg "title=" Address variable. png "alt=" wkiol1yvkiqzhhwjaaf5cf1mkjg632.jpg "/>

6. Data type

The basic types are: integer, character, and real.

650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M00/74/F9/wKiom1YvkiXQBlXQAAD8LPP4O7Q663.jpg "title=" integral type. png "alt=" Wkiom1yvkixqblxqaad8lpp4o7q663.jpg "/>

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/74/F6/wKioL1Yvkmyjns-LAAJF-CmsEpo751.jpg "title=" Integer table. png "alt=" wkiol1yvkmyjns-laajf-cmsepo751.jpg "/>

The program looks at the number of bytes that long occupies:

printf ("Long =%d\n", sizeof (long));

Character type: Storing characters

The character type takes up one byte, 8 bits, represents the range 0-255, and the range represented is too limited.

Characters commonly used characters:

48-57 0-9

65-90 A-Z

97-122 A-Z

\ nthe line break

\ t transverse jump lattice

\ r Enter

\b Backspace

\ \ counter Slash

Real: Number of digits with a decimal point.

Single-type (float), double type (double), long double type (long doubles)

650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M01/74/F9/wKiom1YvknPQ0olwAAJ5wa7j5f8165.jpg "title=" real type. png "alt=" Wkiom1yvknpq0olwaaj5wa7j5f8165.jpg "/>

7. Conversions between the binaries:

Binary, octal, decimal, hexadecimal are generally included.

Binary: 0, 1

Octal: 0 1 2 3 4 5 6 7

Decimal: 0 1 2 3 4 5 6 7 8 9

Hex: 0 1 2 3 4 5 6 7 8 9 A B C D E F

b means binary, o denotes octal, h is hexadecimal, d denotes decimal

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/74/F6/wKioL1YvksvzbIkKAAG8khJgImA003.jpg "title=" First step. png "alt=" wkiol1yvksvzbikkaag8khjgima003.jpg "/>

How decimal is converted to binary: short Division.

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/74/F9/wKiom1YvkyLSVqz9AABvdZSNjaE226.jpg "title=" Step two. png "alt=" wkiom1yvkylsvqz9aabvdzsnjae226.jpg "/>

The correspondence between binary and octal:

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/74/F9/wKiom1Yvk1uDFWkaAADaW6K2X5I643.jpg "title=" Step three. png "alt=" wkiom1yvk1udfwkaaadaw6k2x5i643.jpg "/>

Binary conversion to octal example:

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/74/F6/wKioL1Yvk7aA5gFgAADMm-2NPDk090.jpg "title=" Fourth step. png "alt=" wkiol1yvk7aa5gfgaadmm-2npdk090.jpg "/>

The correspondence between binary and hexadecimal:

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M01/74/F6/wKioL1Yvk-CyUNBhAAFSsycZM7E468.jpg "title=" Fifth step. png "alt=" wkiol1yvk-cyunbhaafssyczm7e468.jpg "/>

Binary conversion to hexadecimal example:

650) this.width=650; "Src=" http://s3.51cto.com/wyfs02/M02/74/F9/wKiom1Yvk9jwaknMAADS1zFIM8I765.jpg " Title= "sixth step. png" alt= "wkiom1yvk9jwaknmaads1zfim8i765.jpg"/>

Introduction to C Language Program first lesson/4