1. Structured Programming (Top Down Step Refinement)
Problem: To count the number of characters, the number of lines, and the number of words in a paragraph of text.
Assumptions:
A word is any sequence of characters that does not contain a blank, tab or newline.
File buffer (text file) format:
xxx...xxx\nxxx...xxx\nxx...xxx\nEOF
White space: blank, tab or newline
Outline:
1. Declaration and initialization
2. Processing
3. Printing results

2. Refinement 1: 2. Processing 2.1 Read one character
2.2 While not end of file do
2.3 Action according to the input character
2.4 Read next character
Variables required:
c to store one character (char)
nc to count the number of characters (int)
nl to count the number of lines (int)
nw to count the number of words (int)

3. Refinement 2: 2.1 c = getchar(); 2.2 while (... != EOF) 2.3
2.3.1 to count the number of characters. nc++;
2.3.2 if c = ‘\n’, to count the number of lines. nl++;
2.3.3 action for white space
2.3.4 actions for non-white space
2.4 c = getchar();
Variable required:
<no extra>

4. Refinement 3: 2.3.3 2.3.3.1 set state = 0 (OUT) 2.3.4
if (state == 0) count one more word nw++;
set state = 1 (IN)
Variable required:
state the state indicates whether you are reading a
word or not. (boolean, int for C)
After you have done the refinements, you can start writing the code for each step.

5. The Final Product --- Program Code
#include <stdio.h>
#define IN 1
#define OUT 0
main() {
int c, nl, nw, nc, state;
nl = nw = nc = state = 0;
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(“nl=%d nw=%d nc=%d\n”, nl, nw, nc);