C/Function/Function
Версия от 14:20, 25 мая 2010; (обсуждение)
Содержание
- 1 A program with two functions
- 2 A simple program that demonstrates sum()
- 3 Assign function return value to a variable
- 4 Check out the int value change before and after function call
- 5 Define function and return value
- 6 Define function and use it
- 7 Define function and use it: square
- 8 Define function to calculate the ounces and cups
- 9 Define function to calculate the volumn
- 10 Define function to multiply two int
- 11 Define function to output char
- 12 Define function to sum
- 13 Define function with parameter and return value
- 14 Define function with void return
- 15 Define two functions and call them in main
- 16 Define two functions and make function call
- 17 Definition of the function to calculate an average
- 18 Demonstraction of function call
- 19 Function call
- 20 Function call each other
- 21 Function declaration
- 22 Function: Print a string in uppercase
- 23 Function prototype
- 24 Function prototype: declare getnum() prior to its first use
- 25 Function to output square
- 26 Function which returns int value
- 27 Global and local variable inside function
- 28 Return statement
- 29 Serve as a prototype within this program
- 30 This program has three functions
- 31 Uses a function prototype to enforce strong type checking
A program with two functions
#include <stdio.h>
void f(void); /* prototype for f() */
int main(void)
{
printf("I ");
f();
printf("java2s.com.");
return 0;
}
void f(void)
{
printf("like ");
}
A simple program that demonstrates sum()
#include <stdio.h>
void sum(int x, int y);
int main(void) {
sum(12, 230);
sum(94, 63);
sum(851, 39);
return 0;
}
void sum(int x, int y)
{
printf("%d ", x + y);
}
Assign function return value to a variable
#include <stdio.h>
int f(void);
int main(void)
{
double answer;
answer = f();
printf("%f", answer);
return 0;
}
int f(void)
{
return 100;
}
Check out the int value change before and after function call
#include <stdio.h>
void f(int *k) {
*k = *k + 10;
}
main () {
int i;
i = 0;
printf (" i before call %d \n", i);
f(&i);
printf ("i after call %d \n", i);
}
Define function and return value
#include <stdio.h>
int f(void);
int main(void)
{
char ch;
ch = f();
printf("%c", ch);
return 0;
}
int f(void)
{
return "a";
}
Define function and use it
#include <stdio.h>
int f(void); /* prototype */
int main(void)
{
int num;
num = f( );
printf("%d", num);
return 0;
}
int f(void)
{
return 10;
}
Define function and use it: square
#include <stdio.h>
int sqr(int x);
int main(void)
{
int t=10;
printf("%d %d", sqr(t), t);
return 0;
}
int sqr(int x)
{
x = x * x;
return( x );
}
Define function to calculate the ounces and cups
#include <stdio.h>
int ounces_to_cups(int o);
int main(void)
{
int ounces;
int cups;
printf("Enter ounces: ");
scanf("%d", &ounces);
cups = ounces_to_cups(ounces);
printf("%d cups", cups);
return 0;
}
int ounces_to_cups(int o)
{
return o / 8;
}
Define function to calculate the volumn
#include <stdio.h>
double volume(double s1, double s2, double s3);
int main(void)
{
double vol;
vol = volume(12.2, 5.67, 9.03);
printf("Volume: %f", vol);
return 0;
}
double volume(double s1, double s2, double s3)
{
return s1 * s2 * s3;
}
Define function to multiply two int
#include <stdio.h>
int mul(int a, int b);
int main(void) {
int x, y, z;
x = 10;
y = 20;
z = mul(x, y); /* 1 */
printf("%d", mul(x,y)); /* 2 */
mul(x, y); /* 3 */
return 0;
}
int mul(int a, int b) {
return a * b;
}
Define function to output char
#include <stdio.h>
void printchar(char ch);
int main(void)
{
printchar("A");
printchar("B");
printchar("C");
return 0;
}
void printchar(char ch)
{
printf("%c", ch);
}
Define function to sum
#include <stdio.h>
int sum(int i1, int i2,int i3)
{
return (i1 + i2 + i3);
}
int main()
{
printf("Sum is %d\n", sum(1, 2, 3));
return (0);
}
Define function with parameter and return value
#include <stdio.h>
double f();
int main(void)
{
printf("%f", f(10.2));
return 0;
}
double f(double num)
{
return num / 2.0;
}
Define function with void return
#include <stdio.h>
void outputnum(int num);
int main(void)
{
outputnum(10);
return 0;
}
void outputnum(int num)
{
printf("%d", num);
}
Define two functions and call them in main
#include <stdio.h>
void f1(void);
void f2(void);
int main(void)
{
f1();
f2();
return 0;
}
void f1(void)
{
printf("f1, ");
}
void f2(void)
{
printf("f2.");
}
Define two functions and make function call
#include <stdio.h>
void f1(void), f2(void);
int main(void) {
f1();
return 0;
}
void f1(void) {
int i;
for(i = 0; i < 10; i++)
f2();
}
void f2(void) {
int i;
for(i = 0; i < 10; i++)
printf("%d ", i);
}
Definition of the function to calculate an average
#include <stdio.h>
float average(float x, float y) {
return (x + y)/2.0f;
}
/* main program - execution always starts here */
void main() {
float average(float x, float y); /* Function prototype */
float value1 = 1.0F;
float value2 = 2.0F;
float r = 0.0F;
r = average(value1, value2);
printf("\nThe average is: %f", r);
}
Demonstraction of function call
void f2(void){
printf ("2 \n");
}
void f1 (void) {
printf ("1 \n");
printf ("1 \n");
f2 ( );
printf ("1 \n");
printf ("1 \n");
}
int main ( )
{
printf ("\n");
printf ("\n");
printf ("\n");
printf ("\n");
printf ("\n");
f1();
printf ("\n");
printf ("\n");
printf ("\n");
printf ("\n");
return 0;
}
Function call
void f(int k) {
k = k + 10;
}
int main ( ) {
int i = 0;
printf ("i before call %d \n", i);
f(i);
printf (" i after call %d \n", i);
}
Function call each other
#include <stdio.h>
void f2(int b);
void f1(int a);
int main(void)
{
f1(30);
return 0;
}
void f1(int a)
{
if( a )
f2( a - 1 );
printf("%d ", a);
}
void f2(int b)
{
printf(" . ");
if(b)
f1( b - 1 );
}
Function declaration
#include <stdio.h>
int area(int l, int w);
int main(void)
{
printf("area is %d", area(100, 130));
return 0;
}
int area(l, w)
int l, w;
{
return l * w;
}
Function: Print a string in uppercase
#include <stdio.h>
#include <ctype.h>
void print_upper(char *string);
int main(void)
{
char s[80];
printf("Enter a string: ");
gets(s);
print_upper(s);
printf("\ns is now uppercase: %s", s);
return 0;
}
void print_upper(char *string)
{
register int t;
for(t=0; string[t]; ++t) {
string[t] = toupper(string[t]);
putchar(string[t]);
}
}
Function prototype
#include <stdio.h>
void f(void);
int main(void)
{
f();
f();
return 0;
}
void f(void)
{
int i = 10;
printf("%d ", i);
}
Function prototype: declare getnum() prior to its first use
#include <stdio.h>
/* declare getnum() prior to its first use */
float getnum(void)
{
float x;
printf("Enter a number: ");
scanf("%f", &x);
return x;
}
int main(void)
{
float i;
i = getnum();
printf("%f", i);
return 0;
}
Function to output square
#include <stdio.h>
void sqrF(int num);
int main(void)
{
sqrF(10.0);
return 0;
}
void sqrF(int num)
{
printf("%d", num * num);
}
Function which returns int value
#include <stdio.h>
int convert(void);
int main(void)
{
printf("%d", convert());
return 0;
}
int convert(void)
{
int dollars;
printf("Enter number of dollars: ");
scanf("%d", &dollars);
return dollars / 8;
}
Global and local variable inside function
#include <stdio.h>
int count; /* global count */
void f(void)
{
int count; /* local count */
count = 100;
printf("count in f() : %d\n", count);
}
int main(void)
{
count = 10;
f();
printf("count in main(): %d\n", count);
return 0;
}
Return statement
#include <stdio.h>
void f(void);
int main(void)
{
f();
return 0;
}
void f(void)
{
printf("Here.");
return; /* return with no value */
printf("Never.");
}
Serve as a prototype within this program
#include <stdio.h>
void f(int a, int b)
{
printf("%d ", a % b);
}
int main(void)
{
f(10,3);
return 0;
}
This program has three functions
#include <stdio.h>
void f1(void); /* prototypes */
void f2(void);
int main(void)
{
f2( );
printf("3");
return 0;
}
void f2(void)
{
f1();
printf("2 ");
}
void f1(void)
{
printf("1 ");
}
Uses a function prototype to enforce strong type checking
void sqr_it(int *i); /* prototype */
int main(void)
{
int x;
x = 10;
sqr_it(x); /* type mismatch */
return 0;
}
void sqr_it(int *i)
{
*i = *i * *i;
}