Several details about C Language

1 sizeof is not a function, but an operator.

 

2. When parsing, the compiler ignores the type name, And the const is near to the person Who modifies the person.

Const int * P; // P variable. The object pointed to by P cannot be changed.

Int const * P; // P variable. The object pointed to by P cannot be changed.

Int * const P; // P is unchangeable, and the object pointed to by P is variable.

Const int * const P; // the pointer P and P point to the object are not changeable

 

3Puts () is applicable when the output content does not include variables or constants, instead of the printf function.

4 The volatile keyword is a type modifier. The type variables it declares can be changed by unknown factors in some compilers, such as operating systems, hardware, or other threads. When the variable declared by this keyword is met, the compilerCodeSo as to provide stable access to special addresses. Example of using this keyword: int volatile nvint when the value of the variable declared by volatile is required, the system always reads data from its memory again, even if the previous command reads data from this place.

generally, volatile is used in the following places: volatile must be added to the variable modified in the interrupt service Program for other programs to detect ;, volatile should be added to the labels shared by all tasks in a multi-task environment. Volatile is also required for the hardware registers mapped to memory, because each read/write to it may have different meanings;