Register variable extern external variable external function, register extern

Register variable extern external variable external function, register extern

Register variable

Ignore this.

Variables defined by the register keyword are directly placed in registers.

A register is a storage unit placed inside the CPU. It is much faster than the memory, so when the program calls the same variable for more than 10000 times, it is declared as a register variable, which will increase the execution speed of the program.

Technology development does not need to write register int I, f = 1;

 

Use the keyword extern for external variables

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# Include <iostream> using namespace std; int fun (int x, int y); int main () {extern int a, B; cout <fun (a, B) <endl; return 0;} int a = 15, B =-7; int fun (int x, int y) {int c; c = x> y? X: y; return c ;}

External Functions

# Include <iostream> using namespace std; int fun (int x, int y); int main () {extern fun (int x, int y ); // The method int a = 15, B =-7; cout <fun (a, B) <endl; return 0;} in the external program is called ;}

Int fun (int x, int y) {int c; c = x> y? X: y; return c ;}