C lang:character input and output

Xx_Introduction

• Character input and output is by more line character conpose of the text flow 
• Define name common use capital  letter,easy read.
• The Standard C Library ----->provide I/O model ------>use character flow way.

Ax_Application

• file copy,charater count,line count,word count

Bx_Method

• I/O model common use getchar and putchar,interactive use of putchar and printf.

  1 getchar()     //read next character
  2 putcahr()     //print next character
  3 printf()        //print next(bunch) character

• File Copy
  • file copy version 1

     1 #include<stdio.h>
     2
     3 int main()
     4 {
     5     int c;
     6
     7     c = getchar();
     8     while(c != EOF){
     9         putchar(c);
    10         c = getchar();
    11     }
    12 }

  • file copy version 2

     1 #include<stdio.h>
     2
     3 int main()
     4 {
     5     int c;
     6
     7     while((c = getchar())!= EOF){
     8         putchar(c);
     9     }
    10 }

    != : unequal to. priority overtop assignment(=)             EOF:end of file

  • Conclusion:computer use bit storage of character and any data type.
  • Assignment can portion of expression.
  • Complex statement simple easy read,but so hard understand.
  • Due to unequal to relational operator(!=) priority not overtop assignment(=),so c expression use bracket.

     1 #include <stdio.h>
     2
     3 int main()
     4 {
     5     int c;
     6
     7     while (c = getchar() != EOF){
     8         printf("%d\n",c);
     9     }
    10     printf("%d - at EOF\n",c);
    11     return 0;
    12 }

    if not use bracket,will priority operation EOF,value by 1,if input end or else print "c - at EOF".

  • Print EOF value programming

    1 #include <stdio.h>
    2
    3 int main()
    4 {
    5     printf("EOF is %d\n",EOF);
    6     return 0;
    7 }

    character constant EOF is in <stdio.h> file definition,value by -1

  • 
  • In other system can by definition other value.

• Charater Count

原文地址：https://www.cnblogs.com/enomothem/p/11632748.html