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

2019年10月09日 | 移动技术网IT编程 | 我要评论

干黄花菜怎么吃,清风笑鸢尾,任峰

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

i/o model common use getchar and putchar,interactive use of putchar and printf.
file copy
charater count
line count
count blanks,tabs,and newlines.
replace string of blanks with a single blank
replace tabs and backspaces with visible characters.
word count
print input one word per line.
getchar and putchar printf().and putch()
!= and ==\=
++ / --
eof
long and double
while and if else
ascii 'a'
|| or ; && and

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

2019年10月09日 | 移动技术网IT编程 | 我要评论

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