C语言基础（一）

源码地址 https://github.com/Wy2160640/C

001.第一个C程序

文件1.c

/* The first C programme */
#include <stdio.h>				/* 包含标准输入输出头文件 */
main()						/* 主函数 */
{
		printf("Hello World!
");	/* 打印输出信息 */
}

 编译运行

gcc 1.c

./a.out

Hello World!

 002.运行多个源文件

文件print.c

#include "print.h"

void printHello()
{
	printf("hello word!
");
}

文件helloword.c

#include "print.h"

int main(void){
	printHello();
	return 0;
}

文件print.h

#include "stdio.h"

void printHello(void);

编译运行

gcc print.c helloword.c

./a.out

003.求整数之积

文件3.c

/* Input two numbers, output the product */
#include <stdio.h>

main()
{
		int x,y,m;				/* 定义整型变量x，y，m */
		printf("Please input x and y
");	/* 输出提示信息 */
		scanf("%d%d",&x,&y);			/* 读入两个乘数，赋给x，y变量 */
		m=x*y;					/* 计算两个乘数的积，赋给变量m */
		printf("%d * %d = %d
",x,y,m);		/* 输出结果 */
}

编译运行

gcc 3.c

./a.out

004.比较实数大小

/* 输入两个浮点数，输出它们中的大数 */
#include <stdio.h>
main()
{
	float x,y,c;				/* 变量定义 */
	printf("Please input x and y:
");	/* 提示用户输入数据 */
	scanf("%f%f",&x,&y);
	c=x>y?x:y;				/* 计算c=max(x,y) */
	printf("MAX of (%f,%f) is %f",x,y,c);	/* 输出c */
}

编译运行

gcc 4.c

./a.out

005.字符的输出

/* */
#include <stdio.h>
main()
{
	char ch,nch;	/* */
	int count;	/* */
	int k;		/* */

	printf("Please input a string with a # in the end.
");
	scanf("%c",&ch);	/* */
	while(ch != '#')	/* */
	{
		if(ch >= '0' && ch <= '9')
		{
			/* */
			count = ch-'0'+1;	/* */
			scanf("%c",&nch);	/* */
			for(k=0;k<count;k++)	/* */
				printf("%c",nch);
		}
		else
			printf("%c",ch);	/* */
		printf(" ");			/* */
		scanf("%c",&ch);		/* */
	}
	printf("#
");				/* */
}

编译运行

gcc 5.c

./a.out

006.显示变量所占字节数

/* 输出不同类型所占的字节数*/
#include <stdio.h>
void main()
{
    /* sizeof()是保留字，它的作用是求某类型或某变量类型的字节数, */
    /* 括号中可以是类型保留字或变量。*/
    /*int型在不同的机器，不同的编译器中的字节数不一样,*/
    /*一般来说在TC2.0编译器中字节数为2,在VC编译器中字节数为4 */
    printf("The bytes of the variables are:
");
    printf("int:%d bytes
",sizeof(int));
    /* char型的字节数为1 */
    printf("char:%d byte
",sizeof(char));
    /* short型的字节数为2 */
    printf("short:%d bytes
",sizeof(short));
    /* long型的字节数为4 */
    printf("long:%d bytes
",sizeof(long));
    /* float型的字节数为4 */
    printf("float:%d bytes
",sizeof(float));
    /* double型的字节数为8 */
    printf("double:%d bytes
",sizeof(double));
    /* long double型的字节数为8或10或12 */
    printf("long double:%d bytes
",sizeof(long double));
    getchar();

}

编译运行

gcc 6.c

./a.out

007.自增自减运算

/* */
#include <stdio.h>
main()
{
	int a=5,b,c,i=10;
	b=a++;
	c=++b;

	printf("a = %d, b = %d, c = %d
",a,b,c);
	printf("i,i++,i++ = %d,%d,%d
",i,i++,i++);
	printf("%d
",++i);
	printf("%d
",--i);
	printf("%d
",i++);
	printf("%d
",i--);
	printf("%d
",-i++);
	printf("%d
",-i--);
	getchar();
}

编译运行

gcc 7.c

./a.out

008.数列求和

#include <stdio.h>
main()
{
	int i,j,n;
	long sum=0,temp=0;

	printf("Please input a number to n:
");
	scanf("%d",&n);
	if(n<1)
	{
		printf("The n must no less than 1!
");
		return;
	}

	for(i=1;i<=n;i++)
	{
		temp=0;
		for(j=1;j<=i;j++)
			temp+=j;
		sum+=temp;
	}
	printf("The sum of the sequence(%d) is %d
",n,sum);
	getchar();
	getchar();
}

 编译运行

gcc 8.c

./a.out

009.乘法口诀表

#include <stdio.h>
#include <conio.h>
void main(void)
{
	int i,j,x,y;
	clrscr();
	printf("

  * * * ³Ë·¨¿Ú¾÷±í * * * 

");
	x=9;
	y=5;
	for(i=1;i<=9;i++)
	{
		gotoxy(x,y);
		printf("%2d ",i);
		x+=3;
	}
	x=7;
	y=6;
	for(i=1;i<=9;i++)
	{
		gotoxy(x,y);
		printf("%2d ",i);
		y++;
	}
	x=9;
	y= 6;
	for(i=1;i<=9;i++)
	{
		for(j=1;j<=9;j++)
		{
			gotoxy(x,y);
			printf("%2d ",i*j);
			y++;
		}
		y-=9;
		x+=3;
	}
	printf("

");
}

编译运行

gcc 9.c

./a.out

010.猜数字游戏

#include <stdio.h>
#include <conio.h>
void main()
{
	int Password=0,Number=0,price=58,i=0;
	clrscr();
	printf("
====This is a Number Guess Game!====
");
	while( Password != 1234 )
	{
		if( i >= 3 )
			return;
		i++;
		puts("Please input Password: ");
		scanf("%d",&Password);
	}

	i=0;
	while( Number!=price )
	{
		do{
			puts("Please input a number between 1 and 100: ");
			scanf("%d",&Number);
			printf("Your input number is %d
",Number);
		}while( !(Number>=1 && Number<=100) );
		if( Number >= 90 )
		{
			printf("Too Bigger! Press any key to try again!
");
		}
		else if( Number >= 70 && Number < 90 )
		{
			printf("Bigger!
");
		}
		else if( Number >= 1 && Number <= 30 )
		{
			printf("Too Small! Press any key to try again!
");
		}
		else if( Number > 30 && Number <= 50 )
		{
			printf("Small! Press any key to try again!
");
		}
		else
		{
			if( Number == price )
			{
				printf("OK! You are right! Bye Bye!
");
			}
			else if( Number < price )
			{
				printf("Sorry,Only a little smaller! Press any key to try again!
");

			}
			else if( Number > price )
				printf(" Sorry, Only a little bigger! Press any key to try again!
");
		}
		getch();
	}
}

编译运行

gcc 10.c

./a.out