Clion and C language

Clion Shortcut key Mac OS

Ctrl+A

Back to the beginning of the line

Ctrl+P

Go back to the end of the previous line

Ctrl+n

Go back to the end of the next line

Ctrl+m

Go back to the brackets in the range , Go back to the brackets in the range

Ctrl+D

Execute code

Ctrl+R

Execute code

*Ctrl+F

Next character

*Ctrl+B

Previous character

Ctrl+G

You can find the same character from the current position

*Ctrl+K

Deletes all subsequent characters from the current cursor position

C Basic knowledge of language

The data shows

Character type constants

Character constants are in single quotes ’‘ A character enclosed , Such as ’a’;
C In language , Characters are in accordance with their corresponding characters ASCII Code value to store , A character takes up a byte ,ASCII Code value common 0~255 individual ,256 It's worth , Be careful A space is also a character .
give an example :

char a = ' ';
printf("the space value is %d\n", a);

We put the space character ‘ ’ There are declared variables a in , Output in integer format , The output is ASCII Code value the value corresponding to the space character 32, Binary representation as :00100000, Take up one character length .

Special character constants

C There is a special class of character constants in languages , They represent control characters or special symbols , Such as carriage return, line feed, backspace, etc , They can't be shown on the screen , Nor can I type... From the screen , But we can use escape characters to represent these controls , The escape character is a backslash "" Followed by a character indicates , As in common use :\a,\b,\f,\n,\r,\t,\v,\,",’,?,\0;
The control characters are 32 individual , From the value from 000 To 031,null yes 000 Null character , and 032 Spaces are characters space. So we're calculating string In length , The number of space characters is also included , And when string constants are stored in memory , The system automatically adds “ String end flag ”, That is to say ASCII The code value is 0 Empty character of null, Use escape characters ’\0’ Express , So we are mainly clear about empty characters and space characters space The difference between .

String constant

String constants are in double quotation marks "" Several characters enclosed , For example, the length of the string is 1 The space character “ ”, Those without a single character in double quotation marks are called empty strings , The length is 0.
When string constants are stored in memory , The system automatically adds “ String end flag ”, That is to say ASCII The code value is 0 Empty character of null, Use escape characters ’\0’ Express , But it doesn't output ’\0’, So the length is n String constant for , In memory n+1 Bytes of storage space .

For strings with escape characters , The escape character should be evaluated as 1 Characters , Just because they don't show , So we use the backslash '' The plus character means they ( However, if the escape character does not match the escape character table, it will be ignored ), Do not participate in length calculation .
for example “AB\n” The length of such a string is 3.

Notice the difference between character constants and string constants , They are expressed in different forms , And the nature of storage is different , character constants ’S’ Occupy 1 Bytes , But string constants "S" Occupy 2 Bytes .

Symbolic constant

A constant represented by a symbol in a program is called a symbolic constant , Such as PI representative 3.14, Its advantage is that when our program needs the value of this symbol , Just modify one place .

C The macro is used to define commands in #define Define symbolic constants , Just like using char Define the same usage as character constants , Only there is no assignment symbol between identifier and Symbolic Constant .