ios-c_day6___ function

2015.1.26

Function: A function called a method, a function, or code reuse code body; a function is called by a function name

//   *

//  ***

// *****

//*******

void print (void)

//{

printf ("*\n");

printf ("***\n");

printf ("*****\n");

printf ("*******\n");

//

return;

//}

//

int add (int a, int b)

//{

return a+b;

//}

INT: return value data type

Add: function name, which is actually the entry address of the function

int a, int b:a, B is the interface of the function, is also the form parameter;

Return: function return value;

The function result is the return value of the function;

Function passing Value: passed by value, equivalent to the value to be passed to assign the parameter form;

int main (int argc, const char * argv[]) {

//

//

Print ();

Print ();

printf ("sum =%d\n", add (3,5));

//

return 0;

//}

Local variables and global variables

A local variable is a variable defined within {};

Scope of the local variable: start at the defined position and end with the corresponding};

The scope of the formal parameter: within the current function;

Actual parameters:

Global variables are variables that are defined outside the function body;

Scope of global variables: starting from the location of the definition or declaration, to the end of the whole source program;

The global variable does not belong to a function, it belongs to the whole source program;

The value of the global variable is easily modified

#include <stdio.h>

#if 0

extern int n;

int func (void)

{

int a=200;

printf ("A=%d\n", a);

for (int i; i<5; i++) {

int m=90;

printf ("welcome\n");

}

return 0;

}

int func1 (void)

{

int n=100;

printf ("n=%d\n", N);

return 0;

}

int changeval (int val)

{

n = val;

return 0;

}

int main (int argc, const char *argv[])

{

int a=20;//local variable

Func ();

a=300;

printf ("A=%d\n", a);

Func1 ();

n=3000;

Func1 ();

Changeval (a);

Func1 ();

int val=300;

Changeval (val);//val argument

Func1 ();

return 0;

}

int n=100;//; global variable

#endif

void Print_time (int hour, int min)

//{

printf ("%02d:%02d\n", Hour, Min);

printf ("%p%p\n", &hour, &min);

return;

//}

//

void print_time1 (int hour, int min)

//{

Print_time (Hour, Min);

//

Return

//}

//

//

int main (int argc,const char *argv[])

//{

//

Print_time (12, 5);

int a=1000;

int b=4000;

//

Print_time (13, 6);

//

Print_time1 (12,7);

//

printf ("A =%d, b=%d\n", A, b);

return 0;

//}

#include "Calculator.h"//contains the header file corresponding to the function of the header file with "" "contains, system-defined header file <> contains

int main (int argc,const char *argv[])

//{

printf ("Add =%d\n", add (3, 5));

printf ("Sub =%d\n", Sub (80, 34));

//

Setnum (200);

int ret = Getnum ();

printf ("ret =%d\n", ret);

//

num= 300;

Welcome;

printf ("min =%d\n", min (3, 5));

printf ("num =%d\n", num);

return 0;

//}

#include "Practice.h"

int main (int argc,const char *argv[])

{

int n;

scanf ("%d", &n);

int ret = IsPrime (n);

if (ret) {

printf ("%d is prime number \ n" and "Nth");

}

else{

printf ("%d is not prime number \ n";

}

printf ("zero =%d\n", Countofzero (n));

return 0;

}

ios-c_day6___ function