习题1
答：
无论使用的是C89还是C99编译e1.c，都没有警告信息；
gcc -Wall -std=c89 -o e1 e1.c
习题2
答：
//输出为
Parkinson's Law:
Work expands so as tofill the time
available for the completion.
习题3
答：
#include <stdio.h>
/*
* Copyright: 2020 by Author Liyang Hao
* File name: e3.c
* Description:《C语言：一种现代方法》第二章练习题3
* Author: Liyang Hao
* Date: 2020/04/12
*
* 编译指令：
* gcc -Wall -std=c89 -o e3 e3.c
* gcc -Wall -std=c99 -o e3 e3.c
*/
int main(void)
{
int height = 8, length = 12, width = 10, volume;
volume = height * length * width;
printf("Dimensions: %dx%dx%d\n", length, width, height);
printf("Volume (cubic inches): %d\n", volume);
printf("Dimensional weight (pounds): %d\n", (volume + 165) / 166);
return 0;
}
习题4
#include <stdio.h>
/*
* Copyright: 2020 by Author Liyang Hao
* File name: e4.c
* Description:《C语言：一种现代方法》第二章练习题4
* Author: Liyang Hao
* Date: 2020/04/12
*
* 编译指令：
* gcc -o e4 e4.c
* gcc -Wall -std=c99 -o e4 e4.c
*/
int main(void)
{
int i1, i2;
float f1, f2;
printf("Uninitialized int test: %d, %d\n", i1, i2);
printf("Uninitialized float test: %f, %f\n", f1, f2);
return 0;
}
如果使用gcc -wall -o e4 e4.c编译，则有警告信息生成：
e4.c:19:45: warning: variable 'i1' is uninitialized when used here [-Wuninitialized]
printf("Uninitialized int test: %d, %d\n", i1, i2);
^~
e4.c:16:8: note: initialize the variable 'i1' to silence this warning
int i1, i2;
^
= 0
e4.c:19:49: warning: variable 'i2' is uninitialized when used here [-Wuninitialized]
printf("Uninitialized int test: %d, %d\n", i1, i2);
^~
e4.c:16:12: note: initialize the variable 'i2' to silence this warning
int i1, i2;
^
= 0
e4.c:20:47: warning: variable 'f1' is uninitialized when used here [-Wuninitialized]
printf("Uninitialized float test: %f, %f\n", f1, f2);
^~
e4.c:17:10: note: initialize the variable 'f1' to silence this warning
float f1, f2;
^
= 0.0
e4.c:20:51: warning: variable 'f2' is uninitialized when used here [-Wuninitialized]
printf("Uninitialized float test: %f, %f\n", f1, f2);
^~
e4.c:17:14: note: initialize the variable 'f2' to silence this warning
float f1, f2;
^
= 0.0
如果使用gcc -o e4 e4.c，则没有警告信息，多次执行编译后的程序，则输出值没有规律：
./e4
Uninitialized int test: 405852197, 32766
Uninitialized float test: -462842252054260350976.000000, 0.000000
➜ chapter2 ./e4
Uninitialized int test: 350928933, 32766
Uninitialized float test: -413554857732317642752.000000, 0.000000
➜ chapter2 ./e4
Uninitialized int test: 311894053, 32766
Uninitialized float test: -283615000784469614185676800.000000, 0.000000
➜ chapter2 ./e4
Uninitialized int test: 327925797, 32766
Uninitialized float test: -6518313815769896594702336.000000, 0.000000
➜ chapter2 ./e4
Uninitialized int test: 204394533, 32766
Uninitialized float test: -1984347388889560852201472.000000, 0.000000
➜ chapter2 ./e4
Uninitialized int test: 91361317, 32766
Uninitialized float test: -29658463795810108671581487104.000000, 0.000000
习题5
不合法的标识符有：100_bottles
习题6
答：很多C的库代码在实现时为了避免与使用者定义的全局符号同名，都采用了双下划线、下划线加大写字母开头之类的怪异命名法，所以要避开这些名字，以减少名字冲突的风险。
习题7
答：for、while
习题8
a=(3*q-p*p)/3;
涉及的token有：
a
=
(
3
*
q
-
p
*
p
)
/
3
;
共14个。
习题9
书写规范：
- 在tokens之间放入空格符，比如在运算符前后放一个空格符等
a = (3 * q - p * p) / 3;
习题10
源文件dweight.c
#include <stdio.h>
int main(void)
{
int height, length, width, volume, weight;
height = 8;
length = 12;
width = 10;
volume = height * length * width;
weight = (volume + 165) / 166;
printf("Dimensions: %dx%dx%d\n", length, width, height);
printf("Volume (cubic inches): %d\n", volume);
printf("Dimensional weight (pounds): %d\n", weight);
return 0;
}
