C lang:character input and output (I/O)

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 = ;
         while (getchar() != EOF)
             ++nc;
         printf("%ld\n",nc-);
         return ;
     }

    ++(--) 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 = ; getchar() != EOF;++nc)
         ;
         printf("%.0f\n", nc-);
         return ;
     }

    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 = ;
         while ((c = getchar()) != EOF)
             if (c == '\n')
                 ++nl;
         printf("%d\n",nl);
         return ;
     }

    ==: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 = ;     /* number of blanks     */
         nt = ;     /* number of tabs       */
         nl = ;     /* number of newlines   */
         while ((c = getchar()) != EOF){
             if ( c == ' ')
                 ++nb;
             if ( c == '\t')
                 ++nt;
             if ( c == '\n')
                 ++nl;
         }
         printf("blanks:%6d\ntabs:%6d\nnewlines:%6d\n", nb, nt, nl);
         return ;
     }

    ....>>>

  • version 2

     #include <stdio.h>
     int main()
     {
         int c, nb, nt, nl;
    
         nb = ;     /* number of blanks     */
         nt = ;     /* number of tabs       */
         nl = ;     /* number of newlines   */
         while ((c = getchar()) != EOF)
             if ( c == ' ')
                 ++nb;
             else ( c == '\t')
                 ++nt;
             else ( c == '\n')
                 ++nl;
    
         printf("blanks:%6d\ntabs:%6d\nnewlines:%6d\n", nb, nt, nl);
         return ;
     }

    but I not  successful execute.

• Replace string of blanks with a single blank
  • version 1

     #include <stdio.h>
     #define NONBLANK 'a'
     int main()
     {
         int c, lastc;
    
         lastc = NONBLANK;
         while (( c = getchar()) != EOF){
             if (c != ' ')
                 putchar(c);
             if (c == ' ')
                 if (lastc != ' ')
                     putchar(c);
             lastc = c;
         }
         return ;
     }

    one if statement control nonblank output.tow if statement deal with blank.three blank check blank is one or more blank.last print c.

  • version 2

     #include<stdio.h>
     #define NONBLANK 'a'
     int main()
     {
         int c, lastc;
    
         lastc = NONBLANK;
         while ((c = getchar()) != EOF ){
             if (c != ' ')
                 putchar(c);
             else if (lastc != ' ')
                 putchar(c);
             lastc = c;
         }
         return ;
     }

    ok,success!

  • version 3

     #include <stdio.h>
    
     #define NONBLANK 'a'
     int main()
     {
         int c, lastc;
    
         lastc = NONBLANK;
         while ((c = getchar()) != EOF){
             if (c != ' ' || lastc != ' ')
                 putchar(c);
             lastc = c;
         }
         return ;
     }

    this method use logic simbol (OR) || realize.

  • 

    ok,this aim at blank deal wilth three method.

• Replace tabs and backspaces with visible characters.
  • Realize

     #include<stdio.h>
     int main()
     {
         int c;
    
         while ((c = getchar())!= EOF){
             if (c == '\t')
                 printf("\\t");
             if (c == '\b')
                 printf("\\b");
             if (c == '\\')
                 printf("\\\\");
             if (c != '\b')
                 if (c != '\t')
                     if (c != '\\')
                         putchar(c);
         }
         return ;
     }

    

    why？//？？？？？？？？？？？？？？？？？？？？？？------------------------------program bug.......I brain in the blue screen.so,go to www.baidu.com to find out.

  • Truth  to version 2

     #include<stdio.h>
     int main()
     {
         int c;
    
         while ((c = getch())!= EOF){              /*getchar not identify keyboard backspace.*/
             if (c == '\t')
                 printf("\\t");
             if (c == '\b')
                 printf("\\b");
             if (c == '\\')
                 printf("\\\\");
             if (c != '\b')
                 if (c != '\t')
                     if (c != '\\')
                         putchar(c);
         }
         return ;
     }

    getchar not catch backspace so,will getchar replace getch. getch() can catch any print behavior.

  • 

    oh,yes!

  • It can also be used if-else. to version 3

     #include <stdio.h>
     int main()
     {
         int c;
    
         while((c = getch())!= EOF)
             if (c == '\t')
                 printf("\\t");
             else if (c == '\b')
                 printf("\\b");
             else if (c == '\\')
                 printf("\\\\");
             else
                 putchar(c);
         return ;
     }

    ok.next is a word count.

• word count
  • count input lines,words and strings number.

     #include <stdio.h>
     #define IN 1
     #define OUT 0
    
     int main()
     {
         int c, nl, nw, nc, state;
    
         state = OUT;
         nl = nw = nc = ;
         while ((c = getchar())!= EOF){
             ++nc;
             if (c == '\n')
                 ++nl;
             if (c == ' ' || c == '\n' || c == '\t')
                 state = OUT;
             else if (state == OUT){
                 state = IN;
                 ++nw;
             }
         }
         printf("lines:%9d\nword:%9d\nstring:%9d\n",nl,nw,nc);
         return ;
     }

    &&:AND  ||: OR , AND higher priority OR. expression from left to right.         a = b = c = 0   if meanwhile include value and assignment two type,order from right to left.

  • 
  • IF statement

     if(expression)
         statement1       /* true */
     else
         statement2       /* false */
     else if (expression){
         statement1       /* true*/
         ...
     }

    true or false.

• Print input one word per line.
  • last practical program.very basis.very important.

     #include<stdio.h>
    
     #define IN 1
     #define OUT 0
    
     int main()
     {
         int c, state;
    
         state = OUT;
         while ((c = getchar()) != EOF){
             if (c == ' ' || c == '\n' || c == '\t'){
                 if (state == IN){
                     putchar('\n');
                     state = OUT;
                 }
             } else if (state == OUT){
                 state = IN;
                 putchar(c);
             } else
                 putchar(c);
         }
         return ;
     }

    state is a BOOL value.

• 

Cx_Conclusion

1. I/O model common use getchar and putchar,interactive use of putchar and printf.
2. File Copy
3. Charater Count
4. Line Count
5. Count blanks,tabs,and newlines.
6. Replace string of blanks with a single blank
7. Replace tabs and backspaces with visible characters.
8. word count
9. Print input one word per line.
10. getchar and putchar printf().and putch()
11. != and ==\=
12. ++ / -- 
13. EOF
14. LONG and DOUBLE
15. while and if else
16. ASCII 'A'
17. || OR  ; && AND