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(2019-10-8 update)
  • Character count version 1

    #include <stdio.h>
    
    int main()
    {
        // version 1
        long nc;
    
        nc = 0;
        while (getchar() != EOF)
            ++nc;
        printf("%ld\n",nc-1);
        return 0;
    }

    ++(--) is operater, be euivalent to eg(nc = nc + 1);impression add one.

  • ++(--) use a prefix effect in variable before add.in suffix it's first call variable before use progressive increase.
  • Long than int more big,long support 32bit int support 16bit,but different system imparity,long in printf use %ld.
  • Character version 2

    #include <stdio.h>
    int main()
    {
        double nc;
        for (nc = 0; getchar() != EOF;++nc)
        ;
        printf("%.0f\n", nc-1);
        return 0;
    }

    double and float use %f format output.double more than float.

  • For circulation a circulation body must exsit,null statement for alone semicolon(;).
  • Important is circulation in execute programs before must judge test condition whether it meets. 
• Line Count
  • mind:line equal to line break number.
  • Line count program

    #include <stdio.h>
    int main()
    {
        int c,nl;
    
        nl = 0;
        while ((c = getchar()) != EOF)
            if (c == '\n')
                ++nl;
        printf("%d\n",nl);
        return 0;
    }

     ==:mean equal.      'A':mean character constant.corresponding ASCII number.

  • 

• Count blanks,tabs,and newlines.
  • 

     

    version 1

  • #include <stdio.h>
    int main()
    {
        int c, nb, nt, nl;
    
        nb = 0;     /* number of blanks     */
        nt = 0;     /* number of tabs       */
        nl = 0;     /* number of newlines   */
        while ((c = getchar()) != EOF){
            if ( c == ' ')
                ++nb;
            if ( c == '\t')
                ++nt;
            if ( c == '\n')
                ++nl;