C语言入门课程学习笔记1

第1课 - 概论

第2课 -helloworld

C程序从main()开始执行，基本执行单位为语句
C程序默认情况下自上向下顺序执行
C程序为单纯的文本文件，无法直接执行
C程序编译后可生成二进制可执行程序

第3课 -数据输出

#include <stdio.h>

int main()
{
    printf("%s\n", "Hello, world!");
    printf("%s = %d\n", "1 + 1", 1 + 1);
    printf("D.T.Software\n");

    return 0;
}

第4课 -数据类型与变量

#include <stdio.h>

int main()
{
    printf("%d\n", 2);
    printf("%f\n", 2.0);
    printf("%c\n", '2');

    return 0;
}

第5课 - 深入数据类型与变量

#include <stdio.h>

int main()
{
    int a = 50000;
    short b = 0;

    int i = 0;
    float f = 0.2;

    printf("a = %d\n", a);
    printf("b = %d\n", b);
    printf("\n");

    b = a;

    printf("a = %d\n", a);
    printf("b = %d\n", b);
    printf("\n");

    b = 30000;
    a = b;

    printf("a = %d\n", a);
    printf("b = %d\n", b);
    printf("\n");
    printf("\n");

    printf("i = %d\n", i);
    printf("f = %f\n", f);
    printf("\n");

    f = 3.14f;
    i = f;

    printf("i = %d\n", i);
    printf("f = %f\n", f);

    return 0;
}



    /*
    output:
a = 50000
b = 0

a = 50000
b = -15536

a = 30000
b = 30000


i = 0
f = 0.200000

i = 3
f = 3.140000
    */

#include <stdio.h>

int main()
{
    int a = 50000;
    short b = 0;

    int i = 0;
    float f = 0.2;

    i = 40000;
    b = (short)i;

    printf("i = %d\n", i);
    printf("b = %d\n", b);
    printf("\n");

    f = 3.1415f;
    a = (int)f;

    printf("f = %f\n", f);
    printf("a = %d\n", a);

    return 0;
}



    /*
    output:
i = 40000
b = -25536

f = 3.141500
a = 3
    */

第6课 - 类型与变量编程练习

#include <stdio.h>

int main()
{
    int a = 10;
    int b = 20;

    int c;

    printf("a = %d\n", a);
    printf("b = %d\n", b);

    printf("\n");

    c = a;
    a = b;
    b = c;

    printf("a = %d\n", a);
    printf("b = %d\n", b);

    return 0;
}

#include <stdio.h>

int main()
{
    float f = 1.49f;
    float r = 0;

    r = f + 0.5f;
    r = (int)r;

    printf("f = %f\n", f);
    printf("r = %f\n", r);

    return 0;
}

第7课 - 程序中的数据输入

#include <stdio.h>

int main()
{
    float i = 0;

    printf("i = %f\n", i);

    scanf("%f", &i);

    printf("i = %f\n", i);

    return 0;
}



    /*
    output:
i = 0.000000
34
i = 34.000000
    */

#include <stdio.h>

int main()
{
    int i = 0;
    int j = 0;
    int k = 0;

    printf("Input 2 numbers to add:\n");

    scanf("%d%d", &i, &j);

    k = i + j;

    printf("%d + %d = %d\n", i, j, k);

    return 0;
}



    /*
    output:
Input 2 numbers to add:
23 34
23 + 34 = 57
    */