5,6章

/*  用格雷戈里公式计算π的近似值， 精度为e  */
#include<stdio.h>
#include<math.h>
int main(void)
{
    double e,pi;
    double funpi(double e);


    printf("Enter e:");
    scanf("%lf",&e);
    pi=funpi(e);
    printf("pi=%f\n",pi);


    return 0;
}


double funpi(double e)
{
    int denominator,flag;
    double item,sum;


    flag=1;
    denominator=1;
    item=1.0;
    sum=0;


    /*  当|item| >e时， 执行循环 */
    while(fabs(item)>=e){
        item=flag*1.0/denominator;
        sum=sum+item;
        flag=-flag;
        denominator=denominator+2;
    }

    return sum*4;
}

/* 输出数字金字塔 */
#include<stdio.h>
int main(void)
{
    void pyramid(int n);


    pyramid(5);


    return 0;
}
void pyramid(int n)
{
    int i,j;


    for(i=1;i<=n;i++){
        for(j=1;j<=n-i;j++)
            printf(" ");
        for(j=1;j<=i;j++)
            printf("%d",i);
        putchar('\n');
    }
}

#include<stdio.h>
float result_real,result_imag;
int main(void)
{
    float imag1,imag2,real1,real2;
        /*  函数声明  */
    void complex_prod(float reai1,float imag1,float real2,float imag2);
    void complex_add(float real1,float imag1,float real2,float imag2);


    printf("Enter 1st complex number(real and imaginary):");
    scanf("%f",&real1,&imag1);
    printf("Enter 2nd complex number(real and imaginary):");
    scanf("%f%f",&real2,&imag2);
    complex_add(real1,imag1,real2,imag2);
    printf("addition of complex is %f+%fi\n",result_real,result_imag);
    complex_prod(real1,imag1,real2,imag2);
    printf("product of complex is %f+%fi\n",result_real,result_imag);


    return 0;
}
    /* 定义求复数之和函数 */
void complex_add(float real1,float imag1,float real2,float imag2)
{
    result_real=real1+real2;
    result_imag=imag1+imag2;
}
    /* 定义求复数之积函数 */
void complex_prod(float real1,float imag1,float real2,float imag2)
{
    result_real=real1*real2-imag1*imag2;
    result_imag=real1*imag2+real2*imag1;
}

#include<stdio.h>
int x;
int f();
int main(void)
{
    int a=1;


    x=a;
    a=f();
    {
        int b=2;
        b=a+b;
        x=x+b;
    }
    printf("%d%d",a,x);


    return 0;
}


int f()
{
    int x=4;


    return 0;
}

#include<stdio.h>
double fact_s(int n);
int main(void)
{
    int i,n;
    printf("Input n:");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        printf("%3d!=%.of\n",fact_s(i));


    return 0;
}
double fact_s(int n)
{
    static double f=1;
    f=f*n;


    return(f);
}

#include<stdio.h>
int main(void)
{
      int i;
    char ch_lower,ch_upper;
    for(i=1;i<=6;i++)
    {
        scanf("%c",&ch_lower);
        if(ch_lower>='a'&&ch_lower<='z')
            ch_upper=ch_lower-'a'+'A';
        printf("%c->%c->%d\n",ch_lower,ch_upper,ch_upper%10);
    } 
    return 0;
}

/* 关系运算示例 */
#include<stdio.h>
int main(void)
{
    char ch='w';
    int a=2,b=3,c=1,d,x=10;


    printf("%d",a>b==c);
    printf("%d",d=a>b);
    printf("%d",ch>'a'+1);
    printf("%d",d=a+b>c);
    printf("%d",b-1==a!=c);
    printf("%d\n",3<=x<=5);


    return 0;
}

/* 逻辑运算示例 */
#include<stdio.h>
int main(void)
{
    char ch='w';
    int a=2,b=0,c=0;
    float x=3.0;


    printf("%d",a&&b);
    printf("%d",a||b&&c);
    printf("%d",!a&&b);
    printf("%d",a||3+10&&2);
    printf("%d",!(x==2));
    printf("%d",!x==2);
    printf("%d\n",ch||b);



    return 0;
}

/* 大小写英文字母转换 */
#include<stdio.h>
int main(void)
{
    char ch;


    printf("input characters:");
    ch=getchar();
    while(ch!='\n'){
        if(ch>='A'&&ch<='Z')
            ch=ch-'A'+'a';
        else if(ch>='a'&&ch<='z')
            ch=ch-'a'+'A';
        putchar(ch);
        ch=getchar();
    }
    return 0;
}