A simple tutorial suitable for beginners to get started with C language

A simple tutorial suitable for beginners to get started with C language

CDeclaration of language data variables

The declaration of integer variables uses int, such as: int a;

The declaration of single-precision floating point types uses float, such as: float b;

Use double to declare double-precision floating point type, such as: double c;

CBasic input and output of language

Use scanf() to input data from the keyboard,

The calling format is: scanf(“%d”, &a);scanf(“%f”, &b);scanf(“%lf”, &c) ;

Use printf() to output data to the screen

The calling format is: printf(“%d %f %lf”,a,b,c);

Output “hello world”

#include<stdio.h>
int main()
{
    printf("hello world");
    return 0;
}

Simple numerical calculation:

#include<stdio.h>        //包含一个头文件stdio.h以完成程序的基本输入输出

int main()     //程序主函数，每个程序必须要有的部分

{    //语句框，表示框内的语句属于主函数，在主函数声明的变量只在主函数内部有效

    int a,a1=1;    //声明整形变量a和a1，并直接给a1赋初值为1（使用任何变量都必须先声明后使用）

    a=2;    //给声明过的整形变量a赋值为2

    float b,b1=1.5;   //声明单精度浮点类型变量b和b1，并直接给b1赋初值为1.5

    b=3.5;           //给声明过的单精度浮点数b赋值为3.5

    double c,c1=2.5;   //声明双精度浮点类型变量c和c1，并直接给c1赋初值为2.5

    c=4.5;            //给声明过的双精度浮点数c赋值为4.5

    double d=a+b+c+a1+b1+c1;   //声明一个双精度浮点数d，并把a+b+c+a1+b1+c1的值赋给d

    printf("%lf",d);     //输出d

    scanf("%d %f %lf",&a,&b,&c);   //从键盘上输入三个值，并分别重新赋给a，b，c，其中%d %f %lf称为占位符，其分别为整型、单精度浮点型、双精度浮点型的占位符表示形式

    printf("%d %f %lf",a,b,c);       //输出a,b,c

    return 0;                     //主函数（main函数）结束的标志

}

The difference between single-precision floating-point number (float) and double-precision floating-point number (double):

01.The number of bytes occupied in the memory is different

Single-precision floating-point numbers occupy 4 bytes in the machine’s memory

Double-precision floating-point numbers occupy in the machine’s memory 8 bytes

02.The number of significant digits is different

Single precision floating point number valid digits8digits

Double precision floating point number valid digits 16bit

03.Value range

The representation range of single-precision floating-point numbers: -3.40E 38~3.40E 38

Double-precision floating-point numbers The representation range: -1.79E 308~-1.79E 308

04. in the program Processing speeds vary

Generally speaking,CPUprocesses single-precision floating-point numbers faster than double-precision floating-point numbers

Thank you all for reading, I hope you will benefit a lot.

This article is reproduced from: https://blog.csdn.net/qq_40907279/article/details/81514459

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