beginner help loops

aadil7 · 03-14-2010, 10:50 AM

hi
well ive only just started c programming and i thought the best place to start was hello world so i just thought i would build on that but i seem to have hit a brick wall and i wondered if anyone could help

heres how far ive got so far and basically im getting stuck on if the user enters 0
i want the program to loop around back to the start but i have no clue on how to do that!
ive tried a few different loops and also tried using it in the IF statements, but no give

when i execute this code and enter 0 it continually repeats "x (0) is null please try again" and does not loop back, instead i have to stop the whole program, i guess it kinda like crashes

thanks loads (in advance)

Code:

#include <stdio.h>
#include "simpleio.h"

int main()
{
	int x, i;
	printf("Hello World \n");
	printf("Enter an integer \n");
	x = getInt();
	printf("Value of X = %d \n",x);
	printf("x is stored at: %p\n",&x);
	
	for(i=0;x==0;i++)
	{
		printf("x (%d) is null please try again\n",x); i++;
	}

	if (x>1 && x<10)
	{
		printf("x (%d) is less than 10\n",x);
	}
	
	else
	{
		printf("x (%d) is more than 10\n",x);
	}
	return 0;
}

quzah · 03-14-2010, 11:13 AM

Code:

declare stuff
for( input = getinput(); input != 0; input = getinput() )
{
    ...stuff to repeat...
}

Or...

Code:

declare stuff
do
{
    ...stuff to repeat...
    input = getinput();
} while( input != 0 );

Or...

Code:

declare stuff
while( input != 0 )
{
    ...stuff to repeat...
    input = getinput();
}

Quzah.

UltraKing227 · 03-14-2010, 01:36 PM

some description of the most common loops:

FOR loop:

a FOR loop is used when you want to go from, lets say, number one
to ten. thus looping ten times, but it cant be used to see if number one
is equal to zero or not.

example:

Code:

int i;
for (i = 0; i < 10; i++)
{
 printf("Hello, World!\n");
}

WHILE loop:

a common loop used for checking stuff, like if number one has been pressed
or not. its also the best to use for your problem. example:

Code:

int input;
while(input != 0)
{
 input = getInt();
}

-------
Some final notes:
you can exit a loop by the break; command. example:

Code:

 int i;
for (i = 0; i < 10; i++)
{
 printf("Hello, World!\n");
 if (i == 5)
 {
 break;
 }
}

if you run the code, you will notice that it doesnt print hello,world ten
times anymore. i hoped this helped, if it didnt, feel free to ask.

aadil7 · 03-14-2010, 01:42 PM

Quote:

Originally Posted by UltraKing227

some description of the most common loops:

FOR loop:

a FOR loop is used when you want to go from, lets say, number one
to ten. thus looping ten times, but it cant be used to see if number one
is equal to zero or not.

example:

Code:

int i;
for (i = 0; i < 10; i++)
{
 printf("Hello, World!\n");
}

WHILE loop:

a common loop used for checking stuff, like if number one has been pressed
or not. its also the best to use for your problem. example:

Code:

int input;
while(input != 0)
{
 input = getInt();
}

-------
Some final notes:
you can exit a loop by the break; command. example:

Code:

 int i;
for (i = 0; i < 10; i++)
{
 printf("Hello, World!\n");
 if (i == 5)
 {
 break;
 }
}

if you run the code, you will notice that it doesnt print hello,world ten
times anymore. i hoped this helped, if it didnt, feel free to ask.

thanks for the reply guys

how do you suggest i do this then because if the user enters '0' i want the program to loop to the start so the user starts from the start

aadil7 · 03-14-2010, 01:52 PM

ok i seem to have got around that issue

but i am getting another error now
when i enter a number which is less than 10 it executes the if statement but also loops around
i do not know how this happened :S

Code:

#include <stdio.h>
#include "simpleio.h"

int main()
{
	int x, i;
	printf("Hello World \n");
	printf("Enter an integer \n");
	x = getInt();
	printf("Value of X = %d \n",x);
	printf("x is stored at: %p\n",&x);
	
	do
	{
    	printf("Hello World \n");
	printf("Enter an integer \n");
	x = getInt();
	printf("Value of X = %d \n",x);
	printf("x is stored at: %p\n",&x);
	} 
	while( x == 0 );

	if (x>=1 && x<=10)
	{
		printf("x (%d) is less than 10\n",x);
	}
	
	else
	{
		printf("x (%d) is more than 10\n",x);
	}
	return 0;
}

tabstop · 03-14-2010, 01:55 PM

A do-while loop always executes at least once, since the condition is not checked until the end of the loop.

aadil7 · 03-14-2010, 05:11 PM

Quote:

Originally Posted by tabstop

A do-while loop always executes at least once, since the condition is not checked until the end of the loop.

umm sorry that i dont know but how do i check the condition?

tabstop · 03-14-2010, 05:20 PM

Quote:

Originally Posted by aadil7

umm sorry that i dont know but how do i check the condition?

You enclose it in parentheses after the word "while", as in say

Code:

while (x == 0)

You may be surprised at how much better your program runs if you delete lines seven through eleven.

UltraKing227 · 03-15-2010, 01:31 AM

or, you may do it like this:

Code:

if (x == 0)
{ 
 	do
	{
    	printf("Hello World \n");
	printf("Enter an integer \n");
	x = getInt();
	printf("Value of X = %d \n",x);
	printf("x is stored at: %p\n",&x);
	} 
	while( x == 0 );
}

the above code checks if X is zero or not, if it is then it starts a loop.
otherwise, it just goes ahead. i hope this helped.

vart · 03-15-2010, 01:41 AM

Quote:

Originally Posted by UltraKing227

or, you may do it like this:

Code:

if (x == 0)
{ 
 	do
	{
	} 
	while( x == 0 );
}

how is it better when just using while loop?

03-14-2010, 10:50 AM	#1
aadil7 Registered User Join Date: Mar 2010 Posts: 17	beginner help loops hi well ive only just started c programming and i thought the best place to start was hello world so i just thought i would build on that but i seem to have hit a brick wall and i wondered if anyone could help heres how far ive got so far and basically im getting stuck on if the user enters 0 i want the program to loop around back to the start but i have no clue on how to do that! ive tried a few different loops and also tried using it in the IF statements, but no give when i execute this code and enter 0 it continually repeats "x (0) is null please try again" and does not loop back, instead i have to stop the whole program, i guess it kinda like crashes thanks loads (in advance) Code: #include <stdio.h> #include "simpleio.h" int main() { int x, i; printf("Hello World \n"); printf("Enter an integer \n"); x = getInt(); printf("Value of X = %d \n",x); printf("x is stored at: %p\n",&x); for(i=0;x==0;i++) { printf("x (%d) is null please try again\n",x); i++; } if (x>1 && x<10) { printf("x (%d) is less than 10\n",x); } else { printf("x (%d) is more than 10\n",x); } return 0; }
aadil7 is offline

03-14-2010, 01:36 PM	#3
UltraKing227 Registered User Join Date: Jan 2010 Location: USA, New york Posts: 123	some description of the most common loops: FOR loop: a FOR loop is used when you want to go from, lets say, number one to ten. thus looping ten times, but it cant be used to see if number one is equal to zero or not. example: Code: int i; for (i = 0; i < 10; i++) { printf("Hello, World!\n"); } WHILE loop: a common loop used for checking stuff, like if number one has been pressed or not. its also the best to use for your problem. example: Code: int input; while(input != 0) { input = getInt(); } ------- Some final notes: you can exit a loop by the break; command. example: Code: int i; for (i = 0; i < 10; i++) { printf("Hello, World!\n"); if (i == 5) { break; } } if you run the code, you will notice that it doesnt print hello,world ten times anymore. i hoped this helped, if it didnt, feel free to ask. __________________ Macselent Corp Last edited by UltraKing227; 03-14-2010 at 01:39 PM.
UltraKing227 is offline

03-14-2010, 01:55 PM	#6
tabstop and the Hat of Guessing Join Date: Nov 2007 Posts: 10,163	A do-while loop always executes at least once, since the condition is not checked until the end of the loop.
tabstop is offline

03-15-2010, 01:31 AM	#9
UltraKing227 Registered User Join Date: Jan 2010 Location: USA, New york Posts: 123	or, you may do it like this: Code: if (x == 0) { do { printf("Hello World \n"); printf("Enter an integer \n"); x = getInt(); printf("Value of X = %d \n",x); printf("x is stored at: %p\n",&x); } while( x == 0 ); } the above code checks if X is zero or not, if it is then it starts a loop. otherwise, it just goes ahead. i hope this helped. __________________ Macselent Corp
UltraKing227 is offline

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