C Primer Plu学习笔记【1-4章节】
第一章 复习题
1.对于编程而言，可移植性意味着什么：
答：完善的可移植性程序是，其源代码无须修改就能在不同计算机系统中成功编译的程序。
2.解释源代码文件、目标代码文件和可执行文件有什么区别？
答：源代码文件包含程序员使用的任何编程语言编写的代码。目标代码文件包含机器语言代码，它不必是完整的程序代码。可执行文件包含组成可执行程序的完整机器语言代码。
3.编程的7个步骤
答：1定义程序目标，2设计程序，3编写程序，4编译程序，5运行程序，6测试和调试程序，7维护和修改程序
4.编译器的任务是什么
答：编译器把源代码（如，用C语言写的代码）翻译成等价的机器语言代码（也叫做目标代码）
5.链接器的任务是什么
链接器把编译器编译好的源代码以及库代码和启动代码组合起来，生成一个可执行程序。
2.11复习题
1.C语言的基本模块是什么？
函数
编程题
1。编写程序按照要求输出
#include <stdio.h>
int main(void){
printf("Gustav Mahler\n");
printf("Gustav\nMahle\nr");
printf("Gustav Mahler\n");
return 0;
}
2. 编写一个程序，打印你的姓名和地址
#include <stdio.h>
int main(void){
printf("My name is sidian,age is 18.\n");
return 0;
}
3. 编写一个程序把你的年龄转换成天数
#include <stdio.h>
int main(void){
printf("Days is %d.\n", 18*365);
return 0;
}
4.编写三个函数，用于输出
For he's a jolly good fellow!
For he's a jolly good fellow!
For he's a jolly good fellow!
Which nobody can deny!
#include <stdio.h>
void jolly(void);
void deny(void);
void jolly(void)
{
printf("For he's a jolly good fellow!\n");
}
void deny(void)
{
printf("Which nobody can deny!\n");
}
int main(void)
{
jolly();
jolly();
jolly();
deny();
return 0;
}
5.编写一个程序，生成一下输出:
Brazil, Russia, India, China
India, China,
Brazil, Russia
#include <stdio.h>
void br(void);
void ic(void);
void br(void)
{
printf("Brazil, Russia");
}
void ic(void)
{
printf("India, China");
}
int main(void)
{
br();
printf(", ");
ic();
printf("\n");
ic();
printf(",");
printf("\n");
br();
printf("\n");
return 0;
}
6编写一个程序，创建一个整数变量toes，并将toes设置为10.程序中还有计算toes的两倍和toes的平方。该程序打印3个值，并分别描述已区分。
#include <stdio.h>
int main(void)
{
int toes;
toes = 10;
printf("toes is %d, double toes is %d, toes square is %d.\n",toes,toes*2,toes*toes);
return 0;
}
7.研究表明，微笑好处多多。编写下面的输出
Smile!Smile!Smile!
Smile!Smile!
Smile!
#include <stdio.h>
void smile(void);
void smile(void)
{
printf("Smile!");
}
int main(void)
{
smile();smile();smile();
printf("\n");
smile();smile();
printf("\n");
smile();
printf("\n");
return 0;
}
8.按照标准要求输出
starting now:
one
two
three
done!
#include <stdio.h>
void one_three(void);
void two(void);
void one_three(void)
{
printf("one\n");
two();
printf("three\n");
}
void two(void)
{
printf("two\n");
}
int main(void)
{
printf("starting now:\n");
one_three();
printf("done!\n");
return 0;
}
第三章 数据和C
// platinum.c
#include <stdio.h>
int main(void)
{
float weight;
float value;
printf("Are you worth you weight in platinum?\n");
printf("Let's check it out.\n");
printf("Please enter your weight in pounds: ");
scanf("%f", &weight);
value = 1700.0 * weight * 14.5833;
printf("Your weight in platinum is worth $%.2f.\n",value);
printf("You are easily worth that! If platinum prices drop,\n");
printf("eat more to maintain your value.\n");
return 0;
}
书中的第一个实例代码
格式话参数少些的情况
#include <stdio.h>
int main(void)
{
int ten = 10;
int two = 2;
printf("Doing it right: ");
printf("%d minus %d is %d.\n", ten, 2, ten-two);
printf("Doing it wrong: ");
printf("%d minus %d is %d.\n", ten); /* 少写了两个参数 */
return 0;
}
数值范围的测试
#include <stdio.h>
int main(void)
{
int i = 2147483647;
unsigned int j= 3144960000;
printf("%d, %d, %d\n", i, i+1, i+2);
printf("%d, %d, %d\n", j, j+1, j+2); /* 范围与有符号的一致*/
return 0;
}
格式化8进制，16进制输出
#include <stdio.h>
int main(void)
{
int x = 100;
printf("dec = %d; octal = %o; hex = %x \n",x, x, x);
printf("dec = %d; octal = %#o; hex = %#x \n",x, x, x); /* 数字输出带前置标志格式化输出 */
return 0;
}
打印short,long,long long和unsigned类型
#include <stdio.h>
int main(void)
{
unsigned int un = 3000000000;
short end = 200;
long big = 65537;
long long verybig = 1234567890864200;
char str1[30];
printf("un = %u and not %d\n", un, un); /* %h是short输出方式 */
printf("end = %hd and %d\n", end, end); /* %u是无符号输出，%ld实际测试与lld输出有效位差不多*/
printf("big = %ld and not %hd\n", big, big);
printf("verybig = %lld and not %ld\n", verybig, verybig);
return 0;
}
一般用%d就够用了，整数位情况。
3.4.3 使用字符:char类型
char类型用于存储字符(如，字母或标点符号)，但是从技术层面看，char是整数类型。因为char类型实际上储存的是整数而不是字符。
打印字符
#include <stdio.h>
int main(void)
{
char ch;
printf("Please enter a character. \n");
scanf("%c", &ch);
printf("The code for %c id %d.\n", ch, ch);
return 0;
}
使用了%d格式化输出char
使用inttypes.h文件格式化输出信息
#include <stdio.h>
#include <inttypes.h>
int main(void)
{
int32_t me32;
me32 = 45933945;
printf("First, assume int32_t is int: ");
printf("me32 = %d\n", me32);
printf("Next, Let's not make any assumptions.\n");
printf("Instead, use a \"macro\" from inttyoe.h: ");
printf("me32 = %" PRId32 " \n", me32);
return 0;
}
格式化输出浮点值 %f输出float和double类型浮点数，%e打印指数输出,%a16进制输出
#include <stdio.h>
int main(void)
{
float aboat = 32000.0;
double abet = 2.14e9;
long double dip = 5.32e-5;
// 用科学记数法的输出表示浮点数
printf("%f can be written %e\n",aboat, aboat);
// 控制精度输出
printf("%.2f can be written %.2e\n",aboat, aboat);
// 用16进制的输出表示
printf("And it's %a in hexadecimal, powers of 2 notation\n", aboat);
printf("%f can writen %e\n", abet, abet);
printf("%Lf can be written %Le\n", dip, dip);
return 0;
}
输出
32000.000000 can be written 3.200000e+04 32000.00 can be written 3.20e+04 And it's 0x1.f4p+14 in hexadecimal, powers of 2 notation 2140000000.000000 can writen 2.140000e+09 0.000053 can be written 5.320000e-05 Program ended with exit code: 0
查看各种类型的大小，用内置的函数sizeof
#include <stdio.h>
int main(void)
{
printf("Type int has a size of %zd bytes.\n", sizeof(int));
printf("Type char has a size of %zd bytes.\n", sizeof(char));
printf("Type long has a size of %zd bytes.\n", sizeof(long));
printf("Type long long has a size of %zd bytes.\n", sizeof(long long));
printf("Type float has a size of %zd bytes.\n", sizeof(float));
printf("Type double has a size of %zd bytes.\n", sizeof(double));
printf("Type long double has a size of %zd bytes.\n", sizeof(long double));
return 0;
}
输出
Type int has a size of 4 bytes. Type char has a size of 1 bytes. Type long has a size of 8 bytes. Type long long has a size of 8 bytes. Type float has a size of 4 bytes. Type double has a size of 8 bytes. Type long double has a size of 16 bytes. Program ended with exit code: 0
最后是演示格式化的时候，参数不匹配的情况
#include <stdio.h>
int main(void)
{
int n = 4, m = 5;
float f = 7.0f;
float g = 8.0;
// 多了一个
printf("%d\n", n , m);
printf("%d %d %d\n", n);
// 格式不匹配
printf("%d %d\n", f, g);
return 0;
}
输出
4
4 0 -1125646195
0 0
Program ended with exit code: 0
3.11 编程练习
1.通过试验观察系统如何处理整数上溢、浮点数上溢和浮点数下溢情况。
#include <stdio.h>
#include <math.h>
int main(void)
{
short s1 = 32767;
short res, add_num = 1;
res = s1 + add_num;
float f1 = 999999999.0f;
// 整数上溢
printf("%hd + %d = %d\n", s1 , add_num, res);
// f
printf("%f\n", f1 + 1e399);
printf("%e\n", f1 / 1e399);
printf("\n%f.\n", pow(2.0, 16.0));
printf("short size is %zd.\n", sizeof(short));
return 0;
}
输出
32767 + 1 = -32768 inf 0.000000e+00 65536.000000. short size is 2. Program ended with exit code: 0
2.编写一个程序，要求提示输入一个ASCII码值（），然后打印输出这个字符。
#include <stdio.h>
#include <math.h>
int main(void)
{
int in_num;
printf("Please enter a number:\b\b\b");
scanf("%d", &in_num);
printf("This number %d char is %c.\n",in_num, in_num);
return 0;
}
输出
Please enter a number:99 This number 99 char is c. Program ended with exit code: 0
3 编写一个成后续，发出一个声警报，然后打印下面的文本：
Startled by the sudden sound, Sally shouted,
"By the Great Pumkin, what was that!"
#include <stdio.h>
int main(void)
{
// \a为输出警报音乐
printf("\a");
printf("Startled by the sudden sound, Sally shouted,\n");
printf("\"By the Great Pumkin, what was that!\"\n");
return 0;
}
输出
Startled by the sudden sound, Sally shouted, "By the Great Pumkin, what was that!" Program ended with exit code: 0
4.编写一个程序，读取一个浮点数，先打印成小数点形式，再打印成指数形式。然后，如果系统支持，在打印成p计数法，按照下面格式输出
Enter a floating-point value: 64.25
fixed-point notation: 64.250000
exponential notation: 6.425000e+01
p notation 0x1.01p+6
#include <stdio.h>
int main(void)
{
double f_num;
printf("Enter a floating-point value: ");
scanf("%lf", &f_num);
printf("fixed-point notation: %f\n", f_num);
printf("exponential notation: %e\n", f_num);
printf("p notation %a\n", f_num);
return 0;
}
输出
Enter a floating-point value: 64.25 fixed-point notation: 64.250000 exponential notation: 6.425000e+01 p notation 0x1.01p+6 Program ended with exit code: 0
5.一年大约有3.156X10的7次方秒。编写一个程序，提示用户输入年龄，然后显式该年龄对应的秒速。
#include <stdio.h>
int main(void)
{
double year_second = 3.156e7;
short age;
printf("请输入你的年龄:");
scanf("%hd", &age);
printf("你已经过了%.0f秒了.\n", year_second * age);
return 0;
}
输出
请输入你的年龄:30 你已经过了946800000秒了. Program ended with exit code: 0
6一个水分子的质量为3.0X10的负23次方克。一夸脱水大约950克。编写一个程序，提示用户输入水的夸脱数，变显式水分子的数量。
#include <stdio.h>
int main(void)
{
double l_quality = 3.0e-23;
double in_number;
printf("请输入多少夸脱水:");
scanf("%lf", &in_number);
printf("你输入的%f夸脱水包含%f数量的水分子.\n", in_number,in_number * 950 / l_quality);
return 0;
}
输出
请输入多少夸脱水:.1 你输入的0.100000夸脱水包含3166666666666666881974272.000000数量的水分子. Program ended with exit code: 0
7.一英寸相当于2.54厘米。编写一个程序，提示用户输入身高(/英寸),然后以厘米为单位显式身高。
#include <stdio.h>
int main(void)
{
double in_cm;
printf("请输入你的身高(cm):");
scanf("%lf", &in_cm);
printf("你的身高%f(cm)相当与(%f)(英寸).\n", in_cm,in_cm / 2.54);
return 0;
}
输出
请输入你的身高(cm):180 你的身高180.000000(cm)相当与(70.866142)(英寸). Program ended with exit code: 0
8.一品脱等于2杯，1杯等于8盎司，1盎司等于2汤勺，一汤勺等于3茶勺。编写一个程序，提示用户输入杯数，显式另外不同的等价容量。
#include <stdio.h>
int main(void)
{
double cup_num;
printf("请输入杯数:");
scanf("%lf", &cup_num);
printf("等于%f杯\n", cup_num / 2);
printf("等于%f盎司\n", cup_num * 8);
printf("等于%f汤勺\n", cup_num * 8 * 2);
printf("等于%f茶勺\n", cup_num * 8 * 2 * 3);
return 0;
}
输出
请输入杯数:1.5 等于0.750000杯 等于12.000000盎司 等于24.000000汤勺 等于72.000000茶勺 Program ended with exit code: 0
第4章 字符串和格式化输入/输出
4.1前导程序
#include <stdio.h> #include <string.h> #define DENSITY 62.4 //人体密度 int main() { float weight, volume; int size; unsigned long letters; char name[40]; // name是一个可容纳40个字符的数组 printf("Hi! What's you first name?\n"); scanf("%s", name); // 这里的那么没有用&符号 printf("%s, what's your weight in pounds?\n", name); scanf("%f", &weight); size = sizeof name; letters = strlen(name); volume = weight/ DENSITY; printf("Well, %s, your volume is %2.2f cubic feet.\n", name, volume); printf("Also, your first name has %lu lettrts, \n", letters); printf("and we have %d bytes ti store it.\n", size); return 0; }
输出
Hi! What's you first name?
sidian
sidian, what's your weight in pounds?
150
Well, sidian, your volume is 2.40 cubic feet.
Also, your first name has 6 lettrts,
and we have 40 bytes ti store it.
Program ended with exit code: 0
4.2字符串的介绍，用""告诉编辑器，这是一个字符串。
记住是双引号，单引号就是字符。
4.2.1插入类型数组和null字符
C中的字符串都是以\n结束，这个空字符占用了一个字节。C的字符串是一个数组，数组是同类数据元素的有序序列。
声明字符串如下
char name[40];
跟字符差不多，只不过变量名后面需要添加[]符号
4.2.2使用字符串
重点是scanf当读到制表符，空格，换行后就读取了
示例代码
#include <stdio.h> #define PRAISE "You are an extraordinary being." int main(void) { char name[40]; printf("What's your name? "); scanf("%s", name); printf("Hello, %s. %s\n", name, PRAISE); return 0; }
输出
What's your name? shi jian
Hello, shi. You are an extraordinary being.
Program ended with exit code: 0
"x"与'x'的区别，一个是字符串，一个是字符，最大的区别是字符串里面有两个字符组成。
4.2.3 strlen()函数
#include <stdio.h>
#include <string.h>
#define PRAISE "You are an extraordinary being."
int main()
{
char name[40];
printf("what's your name? ");
scanf("%s", name);
printf("Hello, %s. %s\n", name, PRAISE);
printf("Your name of %zd letters occupies %zd memory cells.\n",
strlen(name), sizeof name); /* strlen 查的是实际的字符串大小，不包括\0， */
printf("The phrase of praise has %zd letters",
strlen(PRAISE));
printf("and occupies %zd memory cells. \n", sizeof(PRAISE));
return 0;
}
输出
what's your name? sidian
Hello, sidian. You are an extraordinary being.
Your name of 6 letters occupies 40 memory cells.
The phrase of praise has 31 lettersand occupies 32 memory cells.
Program ended with exit code: 0
strlen来至string.h文件，可以测试处字符串的实际长度，sizeof可以查寻具体对象或者初始定义的变量空间。
4.3常量和C预处理。
书中介绍了define
#include <stdio.h>
#define PI 3.14159
int main(void)
{
float area, circun, radius;
printf("What is the radius of your pizza?\n");
scanf("%f", &radius);
area = PI * radius * radius;
circun = PI * 2 * radius;
printf("Your basic pizza parameters are as follows:\n");
// 格式化输出通过1.2f保持两位有效小数点，长度为1
printf("circumference = %1.2f, area = %1.2f\n", circun, area);
return 0;
}
输出
What is the radius of your pizza?
6
Your basic pizza parameters are as follows:
circumference = 37.70, area = 113.10
Program ended with exit code: 0
4.3.1 const限定符
const int MONTHS=12;
与define完全不一样的用法
4.3.2 明示常量
C头文件limis.h与float.h分别提供了与整数类型和浮点类型大小限制相关的详细信息。
示例代码
#include <stdio.h> #include <limits.h> #include <float.h> int main(void) { printf("Some number limits for this system:\n"); printf("Biggest int: %d\n", INT_MAX); printf("Smallest long long: %lld\n", LLONG_MAX); printf("One byte = %d bits on this system", CHAR_BIT); printf("Largest double: %e\n", DBL_MAX); printf("Smallest normal float: %e\n", FLT_MIN); printf("float precision = %d digits\n", FLT_DIG); printf("float epsilon = %e\n", FLT_EPSILON); return 0; }
输出
Some number limits for this system:
Biggest int: 2147483647
Smallest long long: 9223372036854775807
One byte = 8 bits on this systemLargest double: 1.797693e+308
Smallest normal float: 1.175494e-38
float precision = 6 digits
float epsilon = 1.192093e-07
Program ended with exit code: 0
4.4 printf()和scanf()
4.4.2 使用printf()
示例代码
#include <stdio.h> #define PI 3.141593 int main(void) { int number = 7; float pies = 12.75; int cost = 7800; printf("The %d contestants ate %f berry pies.\n", number, pies); printf("The value og pi is %f.\n", PI); printf("Farewell! thou art too dear for my possessing,\n"); printf("%c%d\n", '$', 2*cost); return 0; }
输出
The 7 contestants ate 12.750000 berry pies.
The value og pi is 3.141593.
Farewell! thou art too dear for my possessing,
$15600
Program ended with exit code: 0
4.4.3 printf()的转换说明修饰符
示例代码
#include <stdio.h> #define PAGES 959 int main(void) { printf("*%d*\n", PAGES); printf("*%2d*\n", PAGES); printf("*%10d*\n", PAGES); printf("*%-10d*\n", PAGES); // 左对齐 return 0; }
输出
*959*
*959*
* 959*
*959 *
Program ended with exit code: 0
浮点数的格式化输出示例代码:
#include <stdio.h> int main(void) { const double RENT = 3852.99; // 定义常量 printf("*%f*\n", RENT); printf("*%e*\n", RENT); printf("*%4.2f*\n", RENT); printf("*%3.1f*\n", RENT); printf("*%10.3f*\n", RENT); printf("*%10.3E*\n", RENT); printf("*%+4.2f*\n", RENT); printf("*%010.2f*\n", RENT); return 0; }
输出
*3852.990000*
*3.852990e+03*
*3852.99*
*3853.0*
* 3852.990*
* 3.853E+03*
*+3852.99*
*0003852.99*
Program ended with exit code: 0
其他的多种格式化输出
#include <stdio.h>
int main(void)
{
printf("%x %X %#x\n", 31, 31,31);
printf("**%d**% d**% d**\n", 42, 42, -42);
printf("**%5d**%5.3d**%05d**%05.3d**\n", 6, 6, 6, 6);
return 0;
}
输出情况
1f 1F 0x1f
**42** 42**-42**
** 6** 006**00006** 006**
Program ended with exit code: 0
格式化字符串输出，示例代码
#include <stdio.h>
#define BLURE "Authentic imitation"
int main(void)
{
printf("[%2s]\n", BLURE);
printf("[%24s]\n", BLURE);
printf("[%24.5s]\n", BLURE); // .用来限制输出字符串长度
printf("[%-24.5s]\n", BLURE);
return 0;
}
输出
[Authentic imitation]
[ Authentic imitation]
[ Authe]
[Authe ]
Program ended with exit code: 0
学以致用作业
#include <stdio.h>
int main(void)
{
char name[40] = "sidian";
double cash = 1918.66;
printf("The %s family just may be $%.2f richer!\n", name, cash);
return 0;
}
输出
The sidian family just may be $1918.66 richer!
Program ended with exit code: 0
4.4.4转换说明的意义
1、转换不匹配
示例代码，转移不匹配的代码
#include <stdio.h> #define PAGES 336 #define WORDS 65618 int main(void) { short num = PAGES; short mnum = -PAGES; printf("num as short and unsigned short: %hd %hu\n", num, num); printf("-num as short and unsigned short: %hd %hu\n", mnum, mnum); printf("num as int and char: %d %c\n", num, num); printf("WORDS as int, short,and char: %d, %hd, %c\n",WORDS,WORDS,WORDS); return 0; }
输出
num as short and unsigned short: 336 336
-num as short and unsigned short: -336 65200
num as int and char: 336 P
WORDS as int, short,and char: 65618, 82, R
Program ended with exit code: 0
上面的是整形与字节不匹配，下面是浮点数与整数的不匹配。
#include <stdio.h> int main(void) { float n1 = 3.0; double n2 = 3.0; long n3 = 2000000000; long n4 = 1234567890; printf("%.le %.le %.le %.le \n", n1, n2, n3, n4); printf("%ld %ld\n", n3, n4); // 就这个全部正常输出 printf("%ld %ld %ld %ld \n", n1, n2, n3, n4); return 0; }
3e+00 3e+00 0e+00 0e+00
2000000000 1234567890
2000000000 1234567890 -6868094452202405870 77992
Program ended with exit code: 0
2.printf()的返回值
正常返回的是字符数量，错误返回负数
#include <stdio.h> int main(void) { int bph2o = 212; int rv; rv = printf("%d F is water's boiling point.\n", bph2o); /* 包含空格，换行符*/ printf("The printf() function printed %d characters.\n", rv); return 0; }
输出
212 F is water's boiling point.
The printf() function printed 32 characters.
Program ended with exit code: 0
3.打印较长的字符串
3中方法，一种是多次printf打印输出，2是通过\的方式，3是两个字符串之间会自动链接。
#include <stdio.h> int main(void) { printf("Here's one way to print a "); printf("long string.\n"); printf("here's another way to print a \ long string.\n"); printf("Here's the newest way to print a " "long string.\n"); return 0; }
有意思的三种写法，Python里面也是一样的。
4.4.5使用scanf()
一个规则
如果使用scanf()读取基本变量类型的值，再变量名前面加上一个&
如果用scanf()把字符串读取字符串数组中，不要使用&
示例代码
#include <stdio.h> int main(void) { int age; float assets; char pet[30]; printf("Enter your age, assets, and favorute pet.\n"); scanf("%d %f",&age, &assets); scanf("%s", pet); /* 这个不需要加&符号 */ printf("%d $%.2f %s \n",age, assets, pet); return 0; }
输出：
Enter your age, assets, and favorute pet.
22 100 cat
22 $100.00 cat
Program ended with exit code: 0
scanf()函数使用空白(换行符、制表符和空格)把输入分成多个字段。在依次把转换说明和字段匹配时跳过空白。
1.从scanf()角度输入
接下来，我们更详细的研究scanf()如何读取输入。假设scanf（）根据一个%d转换说明读取一个整数。scanf（）函数每次读取一个数字字符或者一个符号(+或-)。如果找到一个数字或者符号，它便保存该字符，并读取下一个字符。如果下一个字符是数字，它便保存该数字并读取下一个字符。scanf()不断地读取和保存字符，直至遇到非数字字符。如果遇到一个非数字字符，它便认为读到了整数的末尾。然后，scanf()把非数字字符放回输入。这意味这程序再下一次读取输入时，首先读到的是上一次读取丢弃的非数字字符。最后，scanf()读取已读取数字(可能还有符号)相应的数值，并将计算后的值放入指定的变量中。
...
3.scanf()的返回值
scanf函数返回成功读取的项数。如果没有读取任何项，且需要读取一个数字而用户却输入一个非数值字符串，scanf()便返回0；
4.4.6printf()和scanf()的修饰符[不知道Python里面能不能用这个格式化输出]
通过输入参数来设定指定的输出宽度
#include <stdio.h> int main(void) { unsigned width, precision; int number = 256; double weight = 242.5; printf("Enter a field width.\n"); scanf("%d", &width); printf("The number is :%*d:\n", width, number); /* 格式化指定输出字符长度*/ scanf("%d %d", &width, &precision); printf("Wright = %*.*f\n", width, precision, weight); printf("Done!\n"); return 0; }
输出
Enter a field width.
6
The number is : 256:
8 3
Wright = 242.500
Done!
Program ended with exit code: 0
scanf的*用法。
#include <stdio.h>
int main(void)
{
int n;
printf("Please enter three integers:\n");
scanf("%*d %*d %d", &n); // 会忽略前面输入的两个数字
printf("The last integer was %d\n", n);
return 0;
}
输出
Please enter three integers:
2014 2015 2016
The last integer was 2016
Program ended with exit code: 0
4.4.7printf()的用法提示
1.通过%数字d来对齐格式化输出
2.浮点数格式话通过%.2f这样就可以了。
4.7 复习题
1. 只能读到名，因为除了%c另外所有的scanf碰到空格都会认为，读到这里结束。[错误]
2.打印的输出为
a. He sold the painting for %234.50.
b. Hi! \41表示8进制下字符的数字表示 ；\x41表示16进制下字符的数字表示
c. His Hamlet was funny weithout being vulgar.
has 42 characters.
d. Is 1.20e3 the same as 1201.00?
3.添加转移\"的符号
4.正确的代码
#include <stdio.h> #define B "booboo" #define X 10 int main(void) { int age, xp; char name[40]; printf("Please enter your first name.\n"); scanf("%s", name); printf("All right, %s, what's your age?\n", name); scanf("%d", &age); xp = age + X; printf("That's a %s! You must be as least %d.\n", B, xp); return 0; }
5.代码如下
# include <stdio.h> #define BOOK "War and Peace" int main(void) { float cost = 12.99; float percent = 80.0; printf("This copy of \"War and Peace\" sell for $ %.2f.\n", cost); printf("That is %.0f%% of list.\n", percent); return 0; }
6.
%d
%4x -> %4X
%10.f -> %10.3f
%012.2e
%-30s
7
%15lu
%4x -> %#4x
%-12.2E
%10.3f ->%+10.3f
%8s -> %8.8s
8
%6.4d
%*o
%2c
%+f -> %+0.2
%-7.5s
9
int num;
scanf("%d", &num);
double num -> float num1, num2;
scanf("%f", &num); scanf("%f %f", &num1, &num2)
char str[40];
scanf("%s", str);
char actiong[20];
int value;
scanf("%s %d", action, &value)
int num;
scanf("%* %d", &num); -> scnaf("%*s %d", &num);
10
空白就是换行符，制表符，空格
编程练习
1.
#include <stdio.h> int main(void) { char second_name[40]; char first_name[40]; printf("请输入你的名与姓:\n"); scanf("%s %s", second_name, first_name); printf("%s,%s\n",second_name, first_name); return 0; }
输出
请输入你的名与姓:
stenv liu
stenv,liu
Program ended with exit code: 0
2.
#include <stdio.h> #include <string.h> int main(void) { char name[40]; int len; printf("Please input your name:\n"); scanf("%s", name); printf("\"%s\"\n", name); printf("\"%20s\"\n", name); printf("\"%-20s\"\n", name); len = (int)strlen(name)+3; printf("\"%*s\"\n",len, name); return 0; }
输出
Please input your name:
sd
"sd"
" sd"
"sd "
" sd"
Program ended with exit code: 0
3
#include <stdio.h> int main(void) { float number; printf("input a float nunber:\n"); scanf("%f", &number); printf("The input is %.1f or %.1e\n", number, number); printf("The input is %+.3f or %.3E\n", number, number); return 0; }
输出
input a float nunber:
21.29
The input is 21.3 or 2.1e+01
The input is +21.290 or 2.129E+01
Program ended with exit code: 0
稍微有点不一样，书中要求，2,129E+001
4.
#include <stdio.h> #define change_unit 12 int main(void) { float height; char name[40]; printf("Please input you name:\n"); scanf("%s", name); printf("please input you height(inches):\n"); scanf("%f", &height); printf("%s, you are %.3f feet tall.\n", name, height/change_unit); return 0; }
输出
Please input you name:
sd
please input you height(inches):
70
sd, you are 5.833 feet tall.
Program ended with exit code: 0
5.
#include <stdio.h> int main(void) { float file_size, speed; printf("input you file_size, speed:\n"); scanf("%f,%f", &file_size, &speed); printf("At %.2f megabits per second, afile of %.2f megabytes\n", speed, file_size); printf("downloads in %.2f sencond.\n", file_size / (speed / 8)); return 0; }
输出
input you file_size, speed:
2.2,18.12
At 18.12 megabits per second, afile of 2.20 megabytes
downloads in 0.97 sencond.
Program ended with exit code: 0
6.
#include <stdio.h> #include <string.h> int main(void) { char second_name[40], first_name[40]; printf("input you second_name:\n"); scanf("%s", second_name); printf("input you first_name:\n"); scanf("%s", first_name); printf("%s %s\n", second_name, first_name); printf("%s %s\n%*d %*d\n", second_name, first_name, strlen(second_name), strlen(second_name), strlen(first_name), strlen(first_name)); printf("%s %s\n%-*d %-*d\n", second_name, first_name, strlen(second_name), strlen(second_name), strlen(first_name), strlen(first_name)); return 0; }
输出
input you second_name:
Melissa
input you first_name:
Honeybee
Melissa Honeybee
Melissa Honeybee
7 8
Melissa Honeybee
7 8
Program ended with exit code: 0
7
#include <stdio.h> #include <float.h> int main(void) { float a=100.0, b=3.0; double c=100.0, d=3.0; printf("float: %.6f %.12f %.16f\n", a/b, a/b, a/b); printf("double: %.6f %.12f %.16f\n", c/d, c/d, c/d); printf("FLT_DIG = %d, DBL_DIG = %d.\n", FLT_DIG, DBL_DIG); return 0; }
输出
float: 33.333332 33.333332061768 33.3333320617675781
double: 33.333333 33.333333333333 33.3333333333333357
FLT_DIG = 6, DBL_DIG = 15.
Program ended with exit code: 0
8.
#include <stdio.h> #define Gallon_conversion_liter 3.785 #define Miles_to_kilometers 1.609 int main(void) { double miles,gallon; printf("Please enter mileage and gas:\n"); scanf("%lf, %lf", &miles, &gallon); printf("%.1lf miles to the gallon.\n", miles/gallon); printf("The fuel consumption of 100 kilometers is %.1lf liters.\n", (gallon * Gallon_conversion_liter) * 100 / (miles * Miles_to_kilometers)); return 0; }
输出
Please enter mileage and gas:
100, 13
7.7 miles to the gallon.
The fuel consumption of 100 kilometers is 30.6 liters.
Program ended with exit code: 0
