My C arrays test program is not working

Question

I am reading The C Programming Language 2nd Edition. I am doing the 2.10 in a tutorial introduction. I have to write a program about arrays. It is supposed to count digits, white spaces and others. This is the program:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
int c, i, nwhite, nother;
int ndigit[10];



nwhite = nother = 0;
for (i = 0; i < 10; ++i)
ndigit[i] = 0;

while ((c = getchar()) != EOF)
if (c >= '0' && c <= '9')
    ++ndigit[c - '0'];
else if (c == ' ' || c == '\n' || c == '\t')
    ++nwhite;
else
    ++nother;

printf("digits =");
for (i = 0; i < 10; ++i)
    printf(" %d ", ndigit[i]);
printf(", white space = %d, other = %d\n", nwhite, nother);
return 0;
}

According to the book, the output of the program by itself is

digits = 9 3 0 0 0 0 0 0 0 1, white space = 123, other = 345

I have 2 questions:

How will the program output by itself without me doing the CTRL+Z?
When I do it manually the output is not right. Please see if I made a mistake in the code.

The output I get is

digits =, white space = 0, other = 0

Compile with all warnings and debug info (e.g. `gcc -Wall -Wextra -g` if using [GCC](http://gcc.gnu.org/)...) then **use the debugger** (e.g. `gdb`). It is an essential skill to have. — Basile Starynkevitch, Dec 28 '14 at 11:12
I get no errors in debugger or build file. I am using Codeblocks — Uddhava Swaminathan, Dec 28 '14 at 11:14
@UddhavaSwaminathan: Then please go seek help with your malfunctioning debugger; it is obvious you badly need it. Stop cursing the nail; fix the hammer! — Ruud Helderman, Dec 28 '14 at 11:27
@Ruud He is probably assuming that a debugger is a program which gives you a list of problems in your code. :-) — Masked Man, Dec 28 '14 at 11:35
@Ruud: I understand what you mean. My debugger says the code is correct. It does not know what output I want and how to make that happen. — Uddhava Swaminathan, Dec 28 '14 at 11:36
@UddhavaSwaminathan I have yet to come across a debugger which says "the code is correct". Could you please tell me what debugger you use? I think I would find such a debugger pretty useful. — Masked Man, Dec 28 '14 at 11:39
@UddhavaSwaminathan You need to first learn how to use a debugger. I am afraid this is definitely how a debugger is meant to be used. The debugger is not a tool which "knows what output you want" and it is certainly not one which knows "how to make it happen". — Masked Man, Dec 28 '14 at 11:42
possible duplicate of [I'm getting the wrong output from a program example in k & r chapter 1.6](http://stackoverflow.com/questions/14299614/im-getting-the-wrong-output-from-a-program-example-in-k-r-chapter-1-6) — Spikatrix, Dec 28 '14 at 11:44
@UddhavaSwaminathan ,How do you compile and run your program? — Spikatrix, Dec 28 '14 at 12:00
@CoolGuy In CodeBlocks I click build then I look for errors and warnings and then click run..... — Uddhava Swaminathan, Dec 28 '14 at 12:04
@UddhavaSwaminathan ,I'm sorry. I've never used Code:Blocks IDE. Try searching how to redirect input and you'll find pages like [this](http://stackoverflow.com/questions/13295869/code-blocks-redirecting-input-output). Try doing ` — Spikatrix, Dec 28 '14 at 12:09
Please stop answering to this question. Thanks for the help handed — Uddhava Swaminathan, Dec 28 '14 at 12:12
@UddhavaSwaminathan: Just to get you on your way: please read http://stackoverflow.com/questions/3974230/how-to-learn-debugging . Find out about single-stepping and breakpoints in your particular debugger; read a manual if necessary. Practice a lot with single-stepping and breakpoints on your program, with small amounts of input data (otherwise single-stepping becomes a tedious job). If possible, find somebody with experience to sit down with you. — Ruud Helderman, Dec 28 '14 at 12:19

unwind · Answer 1 · 2014-12-28T13:31:28.030

4

This:

printf("digits =");
for (i = 0; i < 0; ++i)
    printf(" %d ", ndigit[i]);

has a broken middle part in the for loop's header; i < 0 will not be true (ever!) so the loop will not run.

edited Dec 28 '14 at 13:31

answered Dec 28 '14 at 11:10

unwind

391,730
64
469
606

It is i < 10 Please see closer or please mention the line in which you see the mistake – Uddhava Swaminathan Dec 28 '14 at 11:12
1

See your last for loop – wingerse Dec 28 '14 at 11:15
Please stop answering to this question. Thanks for the help handed – Uddhava Swaminathan Dec 28 '14 at 12:16
`i` is a signed int so eventually it will stop (well, unless the contents of the loop doesn't make it prematurely crash). – Jongware Dec 28 '14 at 14:34

score 2 · Answer 2 · answered Dec 28 '14 at 11:08

2

for (i = 0; i < 0; ++i)

This is wrong.

answered Dec 28 '14 at 11:08

ouah

142,963
15
272
331

Please mention the correct code – Uddhava Swaminathan Dec 28 '14 at 11:10
5

@UddhavaSwaminathan No, I let it as an exercise. – ouah Dec 28 '14 at 11:12
It is i < 10 Please see closer or please mention the line in which you see the mistake – Uddhava Swaminathan Dec 28 '14 at 11:12
1

No, it is `i<0` in the 4th last line – Basile Starynkevitch Dec 28 '14 at 11:13
It gives a similar output as given in the book but not the right one – Uddhava Swaminathan Dec 28 '14 at 11:17
Please stop answering to this question. Thanks for the help handed – Uddhava Swaminathan Dec 28 '14 at 12:18

My C arrays test program is not working

2 Answers2