Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 6 ■ Characters
This problem is a bit more difficult than those we have met so far. When faced with such a
problem, it is best to tackle it a bit at a time, solving easier versions of the problem and working
your way up to solving the complete problem.
For this problem, we can first write a program that simply echoes the input without
numbering the lines. When we get this right, we can tackle the job of numbering the lines.
An outline of the algorithm for this first version is the following:
read a character, ch
while ch is not the end-of-file character
print ch
read a character, ch
endwhile
This will maintain the line structure of the data file since, for instance, when \n is read from
the file, it is immediately printed to the screen, forcing the current line to end.
Program P6.10 implements the above algorithm for reading the data from a file and printing
an exact copy on the screen.
Program P6.10
#include <stdio.h>
int main() {
char ch;
FILE *in = fopen("input.txt", "r");
while ((ch = getc(in)) != EOF)
putchar(ch);
fclose(in);
}
Now that we can echo the input, we need only figure out how to print the line numbers.
A simplistic approach is based on the following outline:
set lineNo to 1
print lineNo
read a character, ch
while ch is not the end-of-file character
print ch
if ch is \n
add 1 to lineNo
print lineNo
endif
read a character, ch
endwhile
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