memset各类型的极大极小值

转载来自：https://blog.csdn.net/Vmurder/article/details/46537613

 

链接：

#include <stdio.h>
int main()
{
    puts("转载请注明出处[辗转山河弋流歌 by 空灰冰魂]谢谢");
    puts("网址：blog.csdn.net/vmurder/article/details/46537613");
}

int

”较“的原则：加法不爆。
极大值：0x7f
较大值：0x3f
较小值：0xc0
极小值：0x80

long long

”较“的原则：加法不爆。
极大值：0x7f
较大值：0x3f
较小值：0xc0
极小值：0x80

float

”较“的原则：保证一定位精度。
7f以上一直到be都是-0 (实际上是一个很小的>-1.0的负数)
极大值：0x7f
较大值：0x4f
较小值：0xce
极小值：0xfe
0xff是 -1.#QNAN0000…… (-∞？)

double

”较“的原则：保证一定位精度。
极大值：0x7f
较大值：0x43
较小值：0xc2
极小值：0xfe

实验代码：

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define N 5
using namespace std;
int a[N];
long long b[N];
float c[N];
double d[N];
void _int()
{
    puts("");
    puts("int:");

    puts("");
    memset(a,0x7f,sizeof a);printf("%d\n",a[0]);
    memset(a,0x80,sizeof a);printf("%d\n",a[0]);
    memset(a,0x81,sizeof a);printf("%d\n",a[0]);

    puts("");
    memset(a,0xbf,sizeof a);printf("%d %d\n",a[0],a[0]*2);
    memset(a,0xc0,sizeof a);printf("%d %d\n",a[0],a[0]*2);
    memset(a,0xc1,sizeof a);printf("%d %d\n",a[0],a[0]*2);

    puts("");
    memset(a,0x3e,sizeof a);printf("%d %d\n",a[0],a[0]*2);
    memset(a,0x3f,sizeof a);printf("%d %d\n",a[0],a[0]*2);
    memset(a,0x40,sizeof a);printf("%d %d\n",a[0],a[0]*2);

    puts("");
    memset(a,0x7e,sizeof a);printf("%d\n",a[0]);
    memset(a,0x7f,sizeof a);printf("%d\n",a[0]);
    memset(a,0x80,sizeof a);printf("%d\n",a[0]);
}
void _long()
{
    puts("");
    puts("long long:");

    puts("");
    memset(b,0x7f,sizeof b);printf("%I64d\n",b[0]);
    memset(b,0x80,sizeof b);printf("%I64d\n",b[0]);
    memset(b,0x81,sizeof b);printf("%I64d\n",b[0]);

    puts("");
    memset(b,0xbf,sizeof b);printf("%I64d %I64d\n",b[0],b[0]*2);
    memset(b,0xc0,sizeof b);printf("%I64d %I64d\n",b[0],b[0]*2);
    memset(b,0xc1,sizeof b);printf("%I64d %I64d\n",b[0],b[0]*2);

    puts("");
    memset(b,0x3e,sizeof b);printf("%I64d %I64d\n",b[0],b[0]*2);
    memset(b,0x3f,sizeof b);printf("%I64d %I64d\n",b[0],b[0]*2);
    memset(b,0x40,sizeof b);printf("%I64d %I64d\n",b[0],b[0]*2);

    puts("");
    memset(b,0x7e,sizeof b);printf("%I64d\n",b[0]);
    memset(b,0x7f,sizeof b);printf("%I64d\n",b[0]);
    memset(b,0x80,sizeof b);printf("%I64d\n",b[0]);
}
void _float()
{
    puts("");
    puts("float:");

    puts("");
    memset(c,0xfd,sizeof c);printf("%f\n",c[0]);
    memset(c,0xfe,sizeof c);printf("%f\n",c[0]);
    memset(c,0xff,sizeof c);printf("%f\n",c[0]);

    puts("");
    memset(c,0xcd,sizeof c);printf("%f %f\n",c[0],c[0]*2);
    memset(c,0xce,sizeof c);printf("%f %f\n",c[0],c[0]*2);
    memset(c,0xcf,sizeof c);printf("%f %f\n",c[0],c[0]*2);

    puts("");
    memset(c,0x4e,sizeof c);printf("%f %f\n",c[0],c[0]*2);
    memset(c,0x4f,sizeof c);printf("%f %f\n",c[0],c[0]*2);
    memset(c,0x50,sizeof c);printf("%f %f\n",c[0],c[0]*2);

    puts("");
    memset(c,0x7e,sizeof c);printf("%.15f\n",c[0]);
    memset(c,0x7f,sizeof c);printf("%.15f\n",c[0]);
    memset(c,0x80,sizeof c);printf("%.15f\n",c[0]);
}
void _double()
{
    puts("");
    puts("double:");

    puts("");
    memset(d,0xfd,sizeof d);printf("%lf\n",d[0]);
    memset(d,0xfe,sizeof d);printf("%lf\n",d[0]);
    memset(d,0xff,sizeof d);printf("%lf\n",d[0]);

    puts("");
    memset(d,0xc1,sizeof d);printf("%lf %lf\n",d[0],d[0]*2);
    memset(d,0xc2,sizeof d);printf("%lf %lf\n",d[0],d[0]*2);
    memset(d,0xc3,sizeof d);printf("%lf %lf\n",d[0],d[0]*2);

    puts("");
    memset(d,0x42,sizeof d);printf("%lf %lf\n",d[0],d[0]*2);
    memset(d,0x43,sizeof d);printf("%lf %lf\n",d[0],d[0]*2);
    memset(d,0x44,sizeof d);printf("%lf %lf\n",d[0],d[0]*2);

    puts("");
    memset(d,0x7e,sizeof d);printf("%lf\n",d[0]);
    memset(d,0x7f,sizeof d);printf("%lf\n",d[0]);
    memset(d,0x80,sizeof d);printf("%lf\n",d[0]);
}
int main()
{
    _int();
    _long();
    _float();
    _double();
}