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

     1 #include <stdio.h>
     2 
     3 int main()
     4 {
     5     // version 1
     6     long nc;
     7 
     8     nc = 0;
     9     while (getchar() != eof)
    10         ++nc;
    11     printf("%ld\n",nc-1);
    12     return 0;
    13 }

    ++(--) 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

    1 #include <stdio.h>
    2 int main()
    3 {
    4     double nc;
    5     for (nc = 0; getchar() != eof;++nc)
    6     ;
    7     printf("%.0f\n", nc-1);
    8     return 0;
    9 }

    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

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

     ==:mean equal.      'a':mean character constant.corresponding ascii number.

  • 

• count blanks,tabs,and newlines.
  • 

     

    version 1

  •  1 #include <stdio.h>
     2 int main()
     3 {
     4     int c, nb, nt, nl;
     5 
     6     nb = 0;     /* number of blanks     */
     7     nt = 0;     /* number of tabs       */
     8     nl = 0;     /* number of newlines   */
     9     while ((c = getchar()) != eof){
    10         if ( c == ' ')
    11             ++nb;
    12         if ( c == '\t')
    13             ++nt;
    14         if ( c == '\n')
    15             ++nl;
    16     }
    17     printf("blanks:%6d\ntabs:%6d\nnewlines:%6d\n", nb, nt, nl);
    18     return 0;
    19 }

    ....>>>

  • version 2

     1 #include <stdio.h>
     2 int main()
     3 {
     4     int c, nb, nt, nl;
     5 
     6     nb = 0;     /* number of blanks     */
     7     nt = 0;     /* number of tabs       */
     8     nl = 0;     /* number of newlines   */
     9     while ((c = getchar()) != eof)
    10         if ( c == ' ')
    11             ++nb;
    12         else ( c == '\t')
    13             ++nt;
    14         else ( c == '\n')
    15             ++nl;
    16 
    17     printf("blanks:%6d\ntabs:%6d\nnewlines:%6d\n", nb, nt, nl);
    18     return 0;
    19 }

    but i not  successful execute.

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

     1 #include <stdio.h>
     2 #define nonblank 'a'
     3 int main()
     4 {
     5     int c, lastc;
     6 
     7     lastc = nonblank;
     8     while (( c = getchar()) != eof){
     9         if (c != ' ')
    10             putchar(c);
    11         if (c == ' ')
    12             if (lastc != ' ')
    13                 putchar(c);
    14         lastc = c;
    15     }
    16     return 0;
    17 }

    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

     1 #include<stdio.h>
     2 #define nonblank 'a'
     3 int main()
     4 {
     5     int c, lastc;
     6 
     7     lastc = nonblank;
     8     while ((c = getchar()) != eof ){
     9         if (c != ' ')
    10             putchar(c);
    11         else if (lastc != ' ')
    12             putchar(c);
    13         lastc = c;
    14     }
    15     return 0;
    16 }

    ok,success!

  • version 3

     1 #include <stdio.h>
     2 
     3 #define nonblank 'a'
     4 int main()
     5 {
     6     int c, lastc;
     7 
     8     lastc = nonblank;
     9     while ((c = getchar()) != eof){
    10         if (c != ' ' || lastc != ' ')
    11             putchar(c);
    12         lastc = c;
    13     }
    14     return 0;
    15 }

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

  • 

     ok,this aim at blank deal wilth three method.

• replace tabs and backspaces with visible characters.
  • realize

     1 #include<stdio.h>
     2 int main()
     3 {
     4     int c;
     5 
     6     while ((c = getchar())!= eof){
     7         if (c == '\t')
     8             printf("\\t");
     9         if (c == '\b')
    10             printf("\\b");
    11         if (c == '\\')
    12             printf("\\\\");
    13         if (c != '\b')
    14             if (c != '\t')
    15                 if (c != '\\')
    16                     putchar(c);
    17     }
    18     return 0;
    19 }

    

     

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

  • truth  to version 2

     1 #include<stdio.h>
     2 int main()
     3 {
     4     int c;
     5 
     6     while ((c = getch())!= eof){              /*getchar not identify keyboard backspace.*/
     7         if (c == '\t')
     8             printf("\\t");
     9         if (c == '\b')
    10             printf("\\b");
    11         if (c == '\\')
    12             printf("\\\\");
    13         if (c != '\b')
    14             if (c != '\t')
    15                 if (c != '\\')
    16                     putchar(c);
    17     }
    18     return 0;
    19 }

    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

     1 #include <stdio.h>
     2 int main()
     3 {
     4     int c;
     5 
     6     while((c = getch())!= eof)
     7         if (c == '\t')
     8             printf("\\t");
     9         else if (c == '\b')
    10             printf("\\b");
    11         else if (c == '\\')
    12             printf("\\\\");
    13         else
    14             putchar(c);
    15     return 0;
    16 }

    ok.next is a word count.

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

     1 #include <stdio.h>
     2 #define in 1
     3 #define out 0
     4 
     5 int main()
     6 {
     7     int c, nl, nw, nc, state;
     8 
     9     state = out;
    10     nl = nw = nc = 0;
    11     while ((c = getchar())!= eof){
    12         ++nc;
    13         if (c == '\n')
    14             ++nl;
    15         if (c == ' ' || c == '\n' || c == '\t')
    16             state = out;
    17         else if (state == out){
    18             state = in;
    19             ++nw;
    20         }
    21     }
    22     printf("lines:%9d\nword:%9d\nstring:%9d\n",nl,nw,nc);
    23     return 0;
    24 }

    &&: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

    1 if(expression)
    2     statement1       /* true */
    3 else
    4     statement2       /* false */
    5 else if (expression){
    6     statement1       /* true*/
    7     ...
    8 }

    true or false.

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

     1 #include<stdio.h>
     2 
     3 #define in 1
     4 #define out 0
     5 
     6 int main()
     7 {
     8     int c, state;
     9 
    10     state = out;
    11     while ((c = getchar()) != eof){
    12         if (c == ' ' || c == '\n' || c == '\t'){
    13             if (state == in){
    14                 putchar('\n');
    15                 state = out;
    16             }
    17         } else if (state == out){
    18             state = in;
    19             putchar(c);
    20         } else
    21             putchar(c);
    22     }
    23     return 0;
    24 }

    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