Hello World
说老实的，我敢说基本上所有的程序员都会看到这句话
相比起看到，自己敲出来还是有种莫名其妙的感觉
几十年前，Dennis Ritchie 在发明C的时候，好像也说过这句话
是不是他说的.....好像忘了
emmmmmm.......
总之就好像跟着时代的步伐，一步一步地向前走
#include<stdio.h>
int main ()
{
printf("Hello world");
}虽然只是一个非常简单的小程序，但是所有东西都是从简单的开始的额，不是吗
- // hash sign
- {} Curly Braces
- / Forward Slash
- F11 Compile & Run
- printf print function
Biggest
到了现在，我们需要比较3个数字的大小
这看起来很简单的3个数字来自用户，简单的来说就是用户输入的
这里涉及到大于号和小于号的使用问题
#include<stdio.h>
void main(){
int a;
int b;
int c;
printf ("input 3 number and press enter to next\n");
scanf ("%d",&a);
scanf ("%d",&b);
scanf ("%d",&c);
if(a>b)
{
if(a<c)
{
printf ("Hey the first is the biggest");
}
else
{
printf ("Hey the secone is the biggest");
}
}
else
{
if (b>c)
{
printf ("Hey the secone is the biggest");
}
else
{
printf ("Hey the third is the biggest");
}
}
}
Variable
#include<stdio.h>
void main(){
//set a = 10
//int = integer
int a = 10;//set a = 10
//vriable name -> a
//value -> 10
//how to input a number from user
float f=4.4;//(floating point number)
//read number
//input a vaule from the user
float num;//num doesn't have a vaule
scanf("%f",&num);//save the vaule from user in valiable num
//Ampersand &-¡· Telling C that save the value from user in the memory in the location of num
//& -> address
printf("%f\n",num);
printf("welcome\n");//print welcome
///n -> print welcome and go to next line
printf("%d\n",a);//print a
//d-> format specifier for ini
printf("%f",f);//print f
//f-> fotmat specifier for float
//tell c what is the types of value
//interger -> decimal -> %d (Read : present d)
//what is the types of value
//float-> %f我们遇到了一个很严重的问题！
为什么打出来的数字后面有几个零
数了数，好像都是6个零
为啥啊
因为C只能读懂小数点后面的第六位小数，当我们使用float 的时候
C就会把数字小数化
比如数字是1的话就会变成1.000000
对于int 和 float这两个变量都有最大值
但是现在不需要知道.......
Even&Odd
#include<stdio.h>
void main(){
int a;
int remainder;
scanf("%d",&a);
remainder = a%2;
if (remainder ==0)
{
printf("Hey Number is Even");
}
else
{
printf("Hey Number is odd");
}
}哦对了
在代码的任意地方打上/ ..... /的话
这两个符号中间的内容会被全自动无视掉
还有一件事，上面这个代码中出现了%
这见鬼的玩意一看就知道不好搞
这玩意叫做余数Remainder
打个比方，3%2 就是1, 4%2 就是0
这样就可以用来检验一个数字是Even偶数 还是 Odd奇数
Biggest in 5 numbers
#include<stdio.h>
void main(){
int a,b,c,d,e;
printf ("Enter 5 numbers")
scanf ("%d%d%d%d%d%d",&a,&b,&c,&d,&e)
if (a>b&a>c&a>d&a>e)
{
max = a;
}
else if (b>a&b>c&b>d&b>e)
{
max = b;
}
else if (c>a&c>b&c>d&c>e)
{
max = c;
}
else if (d>a&d>b&d>c&d>e)
{
max = d;
}
else if (e>a&e>b&e>c&e>d)
{
max = e
}
}俗话说，世上有一种东西叫做暴力美学
上面这行代码简直体现的淋漓尽致
当一个数同时满足大于abcd的时候，它当然就是最大的
然后把所有可能尝试一遍，搞定
所以说，你大爷永远是你大爷
Balabalabalabala
#include<stdio.h>
void main(){
int i;
int n = 0;
for (i=1;i>n;i++)
{
printf ("******** * * * \n");
printf ("* * * * * * * \n");
printf ("* * * * * * * \n");
printf ("******** *********** * *********** \n");
printf ("* * * * * * * \n");
printf ("* * * * * * * \n");
printf ("******** * * *********** * * \n");
printf ("\n\n");
}
}说老实的，我这个只是无聊之作
会一直都在balabalabalabala
最原始的时候只写了bala然后加个循环
后来觉得不够酷炫
弄了个更酷炫的bala
在来个循环
get！
Loop inside loop
#include <stdio.h>
main (){
int n;
int j;
int i;
printf ("Enter a number of lines");
scanf("%d",&n);
//line 1 -> 1 number
//line 2 -> 2 number
//line 3 -> 3 number
//line n -> n number
for (i=1;i<=n;i++)
{
for (j=1;j<i;j++)//run the j loop i times
printf ("%d\n",i);
}
printf ("\n");//a new line in i loop
}听过碟中谍吗
听过的话loop中loop也差不多
甚至我们还可以做loop 中loop 中loop 中loop 中loop 中loop 中loop 中（笑）
number pyramid
#include<stdio.h>
void main(){
int a;
int b;
int n;
printf ("enter a number of max line of number");
scanf ("%d",&n);
for (a=1;a<=n;a++)
{
for (b=n;b>=1;b--)
printf ("%d",b);
}
}这玩意会打出来什么东西呢？
1
12
123
1234
12345
123456
1234567
......我认为这是个绝妙的方法来认识循环
基本上看过这个之后，循环都能了解的差不多了
Little Star1
嗯，这玩意打印出来就像这个
* 4 space n-1 i=1- 3 space n-2 i=2
- 2 space n-3 i=3
- 1 space n-4 i=4
- 0 space n-5 i=5
include<stdio.h>
void main ()
{int n; int i; int j; int k; printf ("how much line of * do you want\n"); scanf ("%d",&n); for (i=1;i<=n;i++)//loop for n { for (k=1;k<=n-i;k++)//loop for space { printf (" "); } for (j=1;j<=i;j++)//loop for number of * { printf ("* "); } printf ("\n"); }}
Little Star2
看到上面那个正数的吗
就是正过来的
到过来呢？
简单
#include<stdio.h>
void main ()
{
int n;
int i;
int j;
int k;
printf ("how much line of * do you want \n");
scanf ("%d",&n);
for (i=n;i>=1;i--)//line of loop
{
for (k=1;k<=n-i;k++)
{
printf (" ");
}
for (j=1;j<=i;j++)
{
printf ("* ");
}
printf ("\n");
}
}
Added at every number
这个简单了，我们有了小星星
把小星星换成数字一定超级酷炫
问题是换了之后还得保持一个小星星的基本性质
那就多弄几个循环嘛，简单
write a program to print
1
2 3
4 5 6
7 8 9 10
...
...
the number of lines is
i have 1 loop for row(i loop)
i have 1 loop for columns (j loop)
i 1 to N means->
1 i=1
2 i=2
3 i=3
4 i=4
..... i=n
j from 1 to 10
1 i=1 j=1
2 i=2 j=1 i=2 j=2
3 i=3 j=1 i=3 j=2 i=3 j=3
4 i=4 j=1 i=4 j=2 j=4 i=3 j=4 i=4
..... i=n
#include<stdio.h>
void main (){
int i;
int j;
int N;
int A;//declare the cariables
int number=1;
printf ("How much line do you want\n");
scanf ("%d",&A);
printf ("no no no no , change a number\n");
scanf ("%d",&N);
for (i=1;i<=N;i++)
{
for (j=1;j<=i;j++)
{
printf ("%d\t",number);// \t-> tap space , in c , This is 8 space
// c doesnt know number
number++;
}
printf ("\n");
}
}While loop
#include<stdio.h>
void main ()
{
int i;
int j;
i = 1;
while (j<10)
{
j = 1; //j become 1 again and again
while (j<=i)
{
printf ("%d",i);
j++;
}
printf ("\n");
i++;
}
}这玩意或许可以叫做while in while
while 循环中还有一个while 循环
也就是说只有同时满足外循环和内循环的时候才能走出来
Switch Case
show a memu
1.add +
2.subtract -
3.multiply *
4.divide /
5.modulus %
#include<stdio.h>
void main ()
{
int variable;
int variable2;
int choice;
int result;
do
{
printf ("input a number : ");
scanf ("%d",&variable);
printf ("input another number : ");
scanf ("%d",&variable2);
printf ("choooooooooose a number of that box to do\n");
printf ("***************************************\n");
printf ("1.add\n");
printf ("2.subtract\n");
printf ("3.multiply\n");
printf ("4.divide\n");
printf ("5.modulus\n");
printf ("***************************************\n");
printf ("***********input 0 to exit*************");
scanf ("%d",&choice);
switch (choice)
{
case 1:
{
result = variable + variable2;
printf ("-------------------\n");
printf ("result is :");
printf ("%d\n",result);
printf ("-------------------\n");
break;
}
case 2:
{
result = variable - variable2;
printf ("-------------------\n");
printf ("result is :");
printf ("%d\n",result);
printf ("-------------------\n");
break;
}
case 3:
{
result = variable * variable2;
printf ("-------------------\n");
printf ("result is :");
printf ("%d\n",result);
printf ("-------------------\n");\
break;
}
case 4 :
{
result = variable / variable2 ;
printf ("-------------------\n");
printf ("result is :");
printf ("%d\n",result);
printf ("-------------------\n");
break;
}
case 5:
{
result = variable % variable2;
printf ("-------------------\n");
printf ("result is :");
printf ("%d\n",result);
printf ("-------------------\n");
break;
}
}
}
while (choice != 0);
printf ("-------------------\n");
printf ("result is :");
printf ("%d\n",result);
printf ("-------------------\n");
}Swicth Case 这个玩意每次都让我想起任天堂的Switch游戏机
有一说一，他两还真有点相似
我能够选择其中的一个，拿出来用
其他的就不管不管
哦对了，在后面还可以加上
while (choice != 0);
printf ("show me your id");来表示输入0就退出
Stupid Day
#include<stdio.h>
void main ()
{
int a;
printf ("enter a number of day");
scanf ("%d",&a);
if(0<a && a<8)
{
switch (a)
{
case 1:
{
printf ("Monday");
break;
}
case 2:
{
printf ("Tuesday");
break;
}
case 3:
{
printf("Wednesday");
break;
}
case 4:
{
printf ("Thurday");
break;
}
case 5:
{
printf ("friday");
break;
}
case 6:
{
printf ("Saturday");
break;
}
case 7:
{
printf ("sunday");
break;
}
// default: //if the value does not match any case
// {
// printf ("stupid day");
// break;
// }
}
}
else
{
printf ("stupid day");
}
}我发现我们老师好像蛮喜欢说stupid这个单词的
不过它确实能表达好多意思
好多好多
举个栗子，当用户输入的数字不在列表中的时候，我们可以说stupid input
简单粗暴易懂
Prime Number
#include <stdio.h>
void main()
{
int a;
int b = 2;
int c = 1;
printf ("input number n =");
scanf ("%d",&a);//5
do
{
c = a%b;//1
b++;//3
if (c == 0)
{
printf ("the number is not a prime number");
break;
}
}while (b<a);//3 <81
//false
printf("%d\n",c);
if(c!=0)
{
printf ("the number is a prime number");
}
}
Biggest in 50 number
#include <stdio.h>
void main()
{
int a;
int b = 2;
int c = 1;
printf ("input number n =");
scanf ("%d",&a);//5
do
{
c = a%b;//1
b++;//3
if (c == 0)
{
printf ("the number is not a prime number");
break;
}
}while (b<a);//3 <81
//false
printf("%d\n",c);
if(c!=0)
{
printf ("the number is a prime number");
}
}这个小程序能够通过改变数字N的值来改变来比较多少个数字的值
Functions
#include<stdio.h>
//function declaration -> tell c that there is a function in the code
//Example : void welcome()
//function definition -> tell what the function will do
//Example : void welcome(){ }
// function call -> tell c use the function
//Example : welcome()
void main ()
{
int x=welcome();
printf("%d",x);
}
int welcome()
{
return 3.65;
}
void bye()
{
}这个小程序能够把程序串联起来，并且通过return来进行串联
Return的值能够在程序之间传输
Armstrong Number
听过阿姆斯壮数嘛？什么？？？没听过？
Alt + F4 谢谢
#include<math.h>
void main()
{
int a;
int b;
int d =0;
int num;
printf ("show me your ID = ");
scanf ("%d",&a);
b = a;//153
while (b>0)
{
num = b % 10;//1
b = b/10;//0
d += pow(num,3);//153
}
if (d ==a)
{
printf ("the number is the armstrong number");
}
else
{
printf ("the number is not a armstrong number");
}
}这个小程序能够检测一个数字是否是阿姆斯壮数
如果你不知道什么是阿姆斯壮数？下载来试试看就知道了
Two funtion in one program
这个玩意被大量应用在我们组的project中
因为每个人负责的部分不一样，所以用这个方法来区分和分隔开来
讲道理这个方法在大型项目中有着很强的拓展性
//function is a sub-program that contains one or more statements and it performs some task when
called.
//pre-defined functions :
//User-defined functions : i make my own function, i make my function to do something.
//
#include<stdio.h>
void add()//created by me
//"add" is the name i give it
//i can change "add" to any name
//i tell the meaning of function
//call the function
{
int a,b,result; //local variable
printf ("enter number 1 =");//ONLY USED IN FUNCTION "ADD"
scanf ("%d",&a);
printf ("enter number 2 =");
scanf ("%d",&b);
result = a+b;
printf ("%d\n",result);
//end of function add
}
//i call function add in function main
void main() //created bu Ritchie
{
add();//use function of "add"
printf ("Done!");//print Done! while function is finish
}
简单的来说，就是在main中引一个指针
指针指向function add（这个名字可以完全自定义）
当表述完成后显示Done！
简单的理解
Return value
如果我想要一个数字在不同的function之间跳跃，达到把不同的function串通起来的目的
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