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 character2 putcahr()     //print next character3 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 }

    View Code

    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 }

    View Code

    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 }

    View Code

    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 }

    View Code

    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 }

    View Code

    

     

     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 }

    View Code

    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         else14             putchar(c);15     return 0;16 }

    View Code

    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 }

    View Code

    &&: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 else4     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         } else21             putchar(c);22     }23     return 0;24 }

    View Code

    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

標籤：C

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