Static in C Language

In the C language, the literal meaning of static can easily lead us astray. In fact, it has three functions. (1) first role: Hide. When we compile multiple files at the same time, all global variables and functions without the static prefix are globally visible. I will give an example to illustrate this sentence. We need to compile two source files, a. c and main. c at the same time. The following is the content of a. c # include <cstdio> Add this statement char a = 'a'; // global variablevoid msg () {printf ("Hello \ n ");}
The following is main. in addition to the header file, c must declare the function: void msg (); int main (void) {extern char; // extern variable must be declared before use printf ("% c", a); (void) msg (); return 0 ;}
You may ask: why can the global variables a and msg defined in a. c be used in main. c? As mentioned above, all global variables and functions without the static prefix have global visibility, and other source files can also be accessed. In this example, a is a global variable, msg is a function, and there is no static prefix. Therefore, it is visible to other source files main. c. If static is added, other source files are hidden. For example, if static is added before the definitions of a and msg, main. c will not be able to see them. This feature allows you to define functions with the same name and variables in different files without worrying about name conflicts. Static can be used as the prefix of functions and variables. For a function, the role of static is limited to hiding. For a variable, static has the following two functions. (2) The second role of static is to keep the variable content persistent. Variables stored in the static data area will be initialized at the beginning of the program, which is also the only initialization. There are two types of variables stored in the static storage area: global variables and static variables, but compared with global variables, static can control the visible range of variables. static is used to hide the variables. (3) The third role of static is that the default Initialization is 0. In fact, global variables also have this attribute, because global variables are also stored in the static data zone. In the static data area, the default values of all bytes in the memory are 0x00. In some cases, this feature can reduce the workload of programmers. Finally, we will summarize the three functions of static in one sentence. First, the main function of static is to hide. Secondly, because static variables are stored in the static storage area, they have persistence and default value 0.