本文学习自狄泰软件学院 唐佐林老师的 C语言入门课程，图片全部来源于课程PPT，仅用于个人学习记录

第18课 - signed 与 unsigned

#include <stdio.h>int main()
{short s = 32767;// 0111 1111 1111 1111int i = 2147483647;//  0111 1111 1111 1111 1111 1111 1111 1111short ss = -32768;//1000 0000 0000 0000int ii = -2147483648;//1000 0000 0000 0000 0000 0000 0000 0000 printf("s = %d\n", s);printf("i = %d\n", i);s = s + 1;//1000 0000 0000 0000 i = i + 1;//1000 0000 0000 0000 0000 0000 0000 0000 printf("after:s = %d\n", s);printf("after:i = %d\n", i);printf("ss = %d\n", ss);printf("ii = %d\n", ii);ss = ss - 1;//0111 1111 1111 1111ii = ii - 1;// 0111 1111 1111 1111 1111 1111 1111 1111printf("after:ss = %d\n", ss);printf("after:ii = %d\n", ii);return 0;
}/*output:
s = 32767
i = 2147483647
after:s = -32768
after:i = -2147483648
ss = -32768
ii = -2147483648
after:ss = 32767
after:ii = 2147483647*/

#include <stdio.h>int main()
{unsigned char uc = 128;char c = 128;unsigned ui = 2147483648;signed i = 2147483648;printf("uc = %u\n", uc);printf("c = %d\n", c);printf("ui = %u\n", ui);printf("i = %d\n", i);return 0;
}/*output:
uc = 128
c = -128
ui = 2147483648
i = -2147483648*/

第19课 - 再论数据类型

#include <stdio.h>int main()
{int c = sizeof(char);//1int s = sizeof(short);//2int i = sizeof(s);//4int uc = sizeof(unsigned char);//1int us = sizeof(unsigned short);//2int ui = sizeof(unsigned int);//4printf("c = %d\n", c);printf("s = %d\n", s);printf("i = %d\n", i);printf("sizeof(float) = %d\n", sizeof(float));//4printf("sizeof(double) = %d\n", sizeof(double));//8printf("uc = %d\n", uc);printf("us = %d\n", us);printf("ui = %d\n", ui);return 0;
}/*output:
c = 1
s = 2
i = 4
sizeof(float) = 4
sizeof(double) = 8
uc = 1
us = 2
ui = 4*/

#include <stdio.h>int main()
{long l = -1l;long long ll = 21474836481ll;printf("l = %ld\n", l);printf("sizeof(long) = %d\n", sizeof(long));printf("ll = %lld\n", ll);printf("sizeof(long long) = %d\n", sizeof ll);return 0;
}/*output:
l = -1
sizeof(long) = 4
ll = 21474836481
sizeof(long long) = 8*/

第20课 - 经典问题剖析

a=a+7 √

b=a+b;
a=b; √
a=(int)(12.3/4); √ 强制类型转换
a+7=b+1; × a+7不是变量


D

B


D

输出16

x<0 ,y=-1;
x=0时，y=0;
x>0时,y=1
此为错误答案

x=0,y=-1;
x>0,y=1;
x<0,y=0;

A,此为错误答案
D，else前漏了;

k 2 4
s 1 1+2 1+2+3 6+4 15 1 5 10
j 2 3 4 5 6 4 5 6
B

C

9 6 3
8 5 2
C

第21课 - 程序中的辅助语句（上）

#include <stdio.h>int main()
{int a = 0;int b = 10;a = b = b + 1; // a=>11  b=>11printf("a = %d, b = %d\n", a, b);a += 1;a -= 2;a *= 3;a /= 4;// a => 7printf("a = %d\n", a);/*复合赋值与连续赋值相结合*/a += b -= 1;printf("a = %d, b = %d\n", a, b);return 0;
}/*output:
a = 11, b = 11
a = 7
a = 17, b = 10*/

#include <stdio.h>int main()
{int a = 0;int b = 10;int c = 0;a = (b < 10) ? 1 : 2;printf("a = %d\n", a);(a < 5) ? (a = 5) : (a = 0);printf("a = %d\n", a);/*((a == 5) ? a : b) = 10; // ERROR*/a = b = c = 0;c = (a = 2, b = 3, a + b);printf("a = %d\n", a);printf("b = %d\n", b);printf("c = %d\n", c);c -= a;  // c = c - a;printf("c = %d\n", c);return 0;
}/*output:
a = 2
a = 5
a = 2
b = 3
c = 5
c = 3*/

第22课 - 程序中的辅助语句（下）

#include <stdio.h>int main()
{int a = 0;int c = 1;a = -c++;  // c -> 2printf("a = %d\n", a);//a = +++c; // +(++c); c -> 3//error: lvalue required as increment operand|a = +(++c);printf("a = %d\n", a);a = -c--;  // c -> 2printf("a = %d\n", a);printf("c = %d\n", c);return 0;
}/*output:
a = -1
a = 3
a = -3
c = 2*/

int main()
{int a = 0;int c = 1;if( a + c > 0 ){printf("a = %d, c = %d\n", a, c);goto ELSE;}else{ELSE: printf("%d + %d = %d\n", a, c, a + c);goto FOR;}for(c=10; c>0; c--){FOR:printf("c = %d\n", c);}return 0;
}/*output:
a = 0, c = 1
0 + 1 = 1
c = 1*/