The first learning is the basic grammar of C language, mainly divided into keywords, identifiers, annotations, data, constants, variables.
First, the key word
1 keyword refers to the system default in the C language characters with special meaning
2 keywords are all lowercase letters, a total of 32 keywords (main function "main" int, return), as follows:
Auto double int struct break else long switchcase enum Register typedef CHAR extern return unionconst float short unsigned continue for signed voiddefault goto sizeof volatile does if while Static
Second, identifiers
The 1 identifier is also a special meaning character and is a programmer's custom name and symbol (the keyword is the system C language default).
2 The function of the identifier.
(1) Naming variables, distinguishing different variables.
(2) function naming, easy to distinguish
3 Custom naming of identifiers
(1) Basic principles
① can only be made up of 26 English letters (case sensitive), 0-9 of 10 Arabic numerals, and an underscore
② cannot start with a number
③ cannot use the system comes with the keyword
(2) Perfect specification
① use English words as much as possible. Or Chinese can also be
The ② identifier is made up of multiple letters, except for the first word, and the first letter of each word is capitalized.
Third, comments
1 comments are used to explain the meaning of a line or a code program, do not participate in program compilation, and do not increase the size of the code
2 Single-line comment
A single-line comment starts with two forward slashes (//), can only comment on one line, from//To the end of the line is the contents of the comment
3 Multi-line comments
Multiline comments start with/*, end with */, the contents of/* and/* are commented
Iv. data (static and dynamic)
1. Static data
Data that is stored on the hard disk of the computer is not actively deleted. Generally exists in the form of a file.
2. Dynamic Data
The data that is loaded when the program runs, and the temporary data (Dynamic Data) is automatically eliminated when the computer shuts down.
3, static data and dynamic data under certain conditions, can be converted to each other
4, Data unit size conversion
1 KB = b,1 MB = 1024x768 kb,1 GB = 1024x768 mb,1 TB = 1024x768 GB
V. Constants (fixed data)
Classification
1 integer constant (int), containing all integers
2 floating-point constant (float/double), float: single-precision floating-point type; double-precision floating-point type
3 character constant (char), single character enclosed in single quotation marks, except Chinese.
4 string constants, one or more characters enclosed in double quotation marks, except Chinese.
Vi. variables (data that needs to be changed at a timely time)
1 variables need to be defined first, and memory will be allocated a piece of memory
2 variable definition Format: Variable type variable name (example: int i;)
3 variable Assignment: variable name = numeric value (example: i = 1;)
Changes to the value of the 4 variable will override the value before the variable name.
C Language--basic grammar