beginner help loops

[aadil7]

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)

#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]

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

Or...

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

Or...

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

Quzah.

[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:

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:

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

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

 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]

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:

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:

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

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

 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]

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

#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]

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

[aadil7]

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]

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

while (x == 0)

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

[UltraKing227]

or, you may do it like this:

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]

or, you may do it like this:

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

how is it better when just using while loop?