C programming Loop question?

chibi2666 · 06-09-2009, 12:09 AM

HI,

I am doing self 'C' study from a book I bought.

I have been trying to figure out how to write this into code.

Write a program that has the user input a height and width. Then it draws a rectangle made of #'s.

For example

Enter a height: 3
Enter a width: 5

#####
#####
#####

Could anybody please show me how this is done. Thanks much.

paulsm4 · 06-09-2009, 12:47 AM

Code:

/* "header files" (like "stdio.h") contain definitions needed by the program... */
#include <stdio.h>  

int
main (int argc, char *argv[])
{
  int h, w;   /* Input variables */
  int iret;   /* return value (for error checking) */
  int i, j;   /* Loop counters */

  /* Get input from user */
  printf ("enter a height and width: ");
  iret = scanf ("%d %d", &h, &w);
  if (iret != 2)
  {
    printf ("ILLEGAL INPUT!\n");
    return 1;
  }

  /* Use two nested "for loops" to draw our rectangle */
  for (i=0; i < h; i++)
  {
    for (j=0; j < w; j++)
    {
      printf ("#");
    }
    printf ("\n");
  }

  /* Hasta la bye-bye */
  printf ("\n\nDone.\n");
  return 0;
}

SAMPLE OUTPUT:

Quote:

enter a height and width: 2 3
###
###

Done.

chibi2666 · 06-11-2009, 07:42 AM

HI,

Thanks for the help. Could you help me with this one
What is the value of J++

I think J++ means plus one. What would the output me?

#include <stdio.h>
int main(){
int i=0,j=0,k=0;
while(((i < 5) || (j < 20)) && (k != 5)){
if((j % 3) == 0){
k++;
i = i + 2;
}
i--;
j++;
}
return 1;
}

pixellany · 06-11-2009, 07:53 AM

Please put your code samples in <code> tags---it keeps the formatting and makes it much easier to read.....

"j++" does not have a value. The expression means "increment j after using it".

"++j" means "increment j before using it".

Quote:

What would the output me?

BE?
If you mean what is the output of the code, why not run it and see?

noctilucent · 06-11-2009, 10:59 AM

Hello. What book are you studying [sorry for not providing help]?

chibi2666 · 06-16-2009, 07:12 PM

HI,

After I ran the program I get nothing. Does that mean it will just keep running forever. j++

#include <stdio.h>
int main(){
int i=0,j=0,k=0;
while(((i < 5) || (j < 20)) && (k != 5)){
if((j % 3) == 0){
k++;
i = i + 2;
}
i--;
j++;
}
return 1;
}

Any help would be geat

chibi2666 · 06-16-2009, 07:12 PM

HI,

After I ran the program I get nothing. Does that mean it will just keep running forever. j++

#include <stdio.h>
int main(){
int i=0,j=0,k=0;
while(((i < 5) || (j < 20)) && (k != 5)){
if((j % 3) == 0){
k++;
i = i + 2;
}
i--;
j++;
}
return 1;
}

Any help would be great

Uncle_Theodore · 06-16-2009, 07:41 PM

Quote:

Originally Posted by chibi2666

HI,

After I ran the program I get nothing. Does that mean it will just keep running forever. j++

#include <stdio.h>
int main(){
int i=0,j=0,k=0;
while(((i < 5) || (j < 20)) && (k != 5)){
if((j % 3) == 0){
k++;
i = i + 2;
}
i--;
j++;
}
return 1;
}

Any help would be geat

No, it will not run forever. Eventually the value of k will hit 5 and the loop will exit. If you want some output on the screen, you might want to add something like

printf("i=%d, j=%d, k=%d\n", i, j, k);

right after the line "i = i + 2". It also helps if you include your code into the code tags, it will be more readable, like this:

Code:

#include <stdio.h>
int main(){
  int i=0,j=0,k=0;
  while(((i < 5) || (j < 20)) && (k != 5)){
   if((j % 3) == 0){
     k++;
     i = i + 2;
     printf("i=%d, j=%d, k=%d\n", i, j, k);
   }
   i--;
   j++;
 }
 return 1;
}

Funny that you're returning 1. Is there any particualr reason for that?

Another thing. Try reading your code as if it were just plain text. It's a good way to understand what the program is doing. In your case it will look like this:

Make i, j and k zero, then, while the condition "(i is less than 5 or j is less than 20) and k is not five" is true, do the following:
if j is divisible by three, increment k and add 2 to i.
subtract 1 from i
increment j by one.

Good luck.

graemef · 06-16-2009, 09:15 PM

Just to add to what Uncle_Theodore said about reading the code a good self-test would be to decide what the values of i, j and k would be each time the code prints out the values, and what the final values will be - before you actually run the code. Were you correct? If not why were you wrong? So long as you understand those questions you will have learnt something from the code.