C Programming Language #3

PROGRAMMINGLANGUAGE #3

Input & Output

Keyboard

Monitor

User Interfacee

User interface is the space where interaction

between humans and machines occurs.

3.1 轉換規格3.2 轉換修飾詞3.3 旗標欄位與寬度3.4 精確度欄位3.5 函式scanf()

3.6 特殊的*修飾詞3.8 轉換的意義

Chapter 3

3.1 CONVERSION SPECIFICATION

型態字元 代表意義

%c 單一字元。

%d 十進位整數

%e 科學記號

%E 科學記號

%f 浮數數

%o 八進位數值

%u 十進位數值

%x 十六進位整數

%X 十六進位整數

Example 3-1/* ch3 printfs.c */

#include <stdio.h>#include <stdlib.h> int main(){

char ch1 = 'a', ch2 = 'A';int i = 31, j = -1;float num = 123.456;double num1 = 123.456;char str[30]= "This is a car ... SAAB";

/* output character */printf(" Format conversion...\n\n");printf(" Character : %c %c\n\n", ch1, ch2);

/* output integer number */printf(" Decimal : %d %d\n", i, j);printf(" Unsigned : %u %u\n", i, j);printf(" Octal : %o \n", i);printf(" Hexdecimal : %x \n", i);printf(" Hexdecimal : %X \n\n", i);

/* output float point number */printf(" Float : %f %e %E\n", num, num, num);printf(" Double : %f %e %E\n\n", num1, num1, num1);

/* output string */printf(" String : %s\n\n", str);

/* output % symbol */printf(" Percent : 100%%\n\n");system("PAUSE");return 0;

Console Output

Format conversion...

Character : a A

Decimal : 31 -1Unsigned : 31 4294967295Octal : 37Hexdecimal : 1fHexdecimal : 1F

Float : 123.456001 1.234560e+002 1.234560E+002Double : 123.456000 1.234560e+002 1.234560E+002String : This is a car ... SAAB

Percent : 100%

3.2 CONVERSION SPECIFIERS

欄位 意義

Flags +、-、#、

Width 列印所佔的寬度

Precision 精確度

Size short、long、double

Conversion Specidiers

3.3 FLAG AND WIDTH

Example

printf(“%d”, 100);

printf(“%5d”, 100);

001

001

Flag 意義 預設情況

- 向左靠齊。 向右方對齊

+ 加上正負符號。 負數才有 '-'號

空格 加上空白。 不列印空白

# 列印字首0、0x、或0X。

0 以數字0補足不足的寬度。 以空白補足寬度

/* ch3 flag2.c */

#include <stdio.h>#include <stdlib.h> int main(){

int decimal = 31;

printf("Flags...\n\n");printf("|%d|\n", decimal);printf("|%8d|\n", decimal);printf("|%#8o|\n", decimal);printf("|%#8x|\n", decimal);printf("|%08d|\n", decimal);system("PAUSE");return 0;

}

Console Output

Flags...

|31|| 31|| 037|| 0x1f ||00000031|

3.4 PRECISION

Example

printf(“%8.5f”, 1.4567);

07654.1

/* ch3 width3.c */

#include <stdio.h>#include <stdlib.h> int main(){

double fl = 2.5e5;

printf("|%15f|\n", fl);printf("|%-15.0f|\n", fl);printf("|%-#15.0f|\n", fl);

printf("|%-15.4f|\n", fl);printf("|%-15.4e|\n", fl);system("PAUSE");return 0;

}

Console Output

| 250000.000000||250000 ||250000. ||250000.0000 ||2.5000e+005 |

3.5 SCANF()

scanf

• Reads data from stdin and stores them into the locations pointed by the arguments.

printf

• Writes a formatted string to stdout.

#include <stdio.h>

int main( )

{

int num1;

int num2;

int sum;

printf(“Enter your number”");

scanf(“%d”, &num1);

scanf(“%d“, &num2);

sum = num1 + num2;

printf(“The Sum is %d”, sum);

getch();

return 0;

}

User Interface?

User Interface: Keyboard

User Interface: Monitor

Types of user interfaces in computer

DOS & UNIX

Mac OS & Windows 7

User Interface: Mouse

Other UI?

stdio.h = Standard Input & Output

「標準輸出」（Standard Output）?

「標準輸入」（Standard Input） ?

/* ch3 scanfs.c */

#include <stdio.h>#include <stdlib.h> int main(){

int num1, num2;double fl;char str[20];

printf("Input two number :\n");scanf("%d %d", &num1, &num2);printf(" ===> %d + %d = %d\n\n", num1, num2,

num1+num2);

printf("Input a floating point :\n");scanf("%lf", &fl);printf(" ===> %f is %e\n\n", fl, fl);

printf("Input a string :\n");scanf("%s", str);printf(" ===> %s \n\n", str);printf("Input at most 10 chars :\n");scanf("%10s", str);printf(" ===> %s\n", str);system("PAUSE");return 0;

}

Input two number :14 5060===> 14 + 5060 = 5074

Input a floating point :119.117===> 119.117000 is 1.191170e+002

Input a string :abcdefghijklmnopq===> abcdefghijklmnopq

Input at most 10 chars :abcdefghijklmnopq===> abcdefghij

Console Output

3.6 * SPECIFIER

37

/* ch3 star1.c */

#include <stdio.h>#include <stdlib.h> int main(){

int width, precision;double d_num = 1234.56789;

printf("Source Number : %f\n\n", d_num);printf("Input the width : ");scanf("%d", &width);

printf("\nInput the precision : ");scanf("%d", &precision);

printf("\nFormat ===> \"%%-%d.%df\"\n", width, precision);printf(" Formatted Number:|%-*.*f|\n", width, precision, d_num);system("PAUSE");return 0;

}

Source Number : 1234.567890

Input the width : 15

Input the precision : 4

Format ===> "%-15.4f"Formatted Number : |1234.5679 |

Console Output

3.8 TYPE CONVERSION

/* ch3 cut.c */

#include <stdio.h>#include <stdlib.h> int main(){

short int num = 321;

printf("Decimal : %d\n", num);printf("Character : %c\n", num);system("PAUSE");return 0;

}

65 (‘A’)

0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 12 bytes

0 1 0 0 0 0 0 11 bytes

Binary expression

0 0 0 00 0 0 1 0 1 0 0 0 0 0 1

num = 321

Low byteHigh byte

Decimal : 321

Character : A

num = 321;

3.10 EXERCISE

#include <stdio.h>

#include <stdlib.h>

int main( )

{

double f = 678.90;

printf(“%%f……………….| %f|\n”, f);

printf(“%%3.2f……………….| %3.2f|\n”, f);

printf(“%%7.2f……………….| %7.2f|\n”, f ");

printf(“%%7.0f……………….| %7.0f|\n”, f);

printf(“%%*.1f……………….| %*.1f|\n”, 7, f);

printf(“%%*.*f……………….| %*.*f|\n”, 7, 1, f ");

system(“PAUSE”);

return 0;

}

Homework #3

• 3.11 No.5 (P.29)

• Write or Print in A4Paper

• Name & I.D.

C Programming is Easy!

Any Question?

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