scanf gives me Zero

This function is a simulator for an elevator
But when the user enter the current_floor it starts from Zero not from the current floor

void elevator_running()
{
	int current_floor,next_floor;
		char operation;

		printf("\t\t\t\tWelcome to elevator simulator\n\n");
		//
		printf("Please enter the current floor: ");
		scanf("%d",&current_floor);
		//
		printf("Please enter where do u want to go 'u' for Up- 'd' for Down: ");
		scanf("%s",&operation);
		//
	if (operation=='u')
	{
				printf("\t\t\t\tThe uping elevator is coming\n\n\n");
				//
				printf("\tPlease enter the next floor:  -The current floor is:%d",current_floor);
				//
				scanf("%d",&next_floor);
				//
				if (next_floor>current_floor)
				{
					while(current_floor<next_floor)
					{
						current_floor++;
						printf("Current floor is: %d\n",current_floor);
					};
					if(current_floor==next_floor)
						printf("We have arrived :)");

				}
				//
				else if(next_floor<current_floor)
				{
					printf("The floor should be higher than the current one.....");
				}
				//
			}
	//
			else if(operation=='d')
			{
				printf("\t\t\t\tThe down elevator is coming\n");
			}
	//
			else
			{
				printf("\t\t\t\tProgram ended rerun and choose between u for up and d for down");
			}
	//

}

ne555 (10692)

I don't observe that. Provide a complete testcase, with input and output examples.

nasser (62)

This is the output

Welcome to elevator simulator

Please enter the current floor: 7
Please enter where do u want to go 'u' for Up- 'd' for Down: u
				The uping elevator is coming


	Please enter the next floor: 9
The current floor is: 0
 the next floor is: 9
Current floor is: 1
Current floor is: 2
Current floor is: 3
Current floor is: 4
Current floor is: 5
Current floor is: 6
Current floor is: 7
Current floor is: 8
Current floor is: 9
We have arrived :)

ne555 (10692)

"%s" is for c-strings and will append a terminator character '\0', so you are accessing out of bounds (end up writting the memory where the floor number is stored)
for reading characters you need to use "%c", or better use c++ istreams that are type-safe

nasser (62)

The problem in Line 9 ,The variable current_floor gives me a Zero although after the user enter it

nasser (62)

It's terminated when I replace the "%s" with "%c"
and my problem is that in line 9 the user should enter the current floor but in line 18 it gives me Zero for the current floor and start couting from 1 in line 24

ne555 (10692)

Sorry, I didn't check the solution. "%c" will match the line break '\n' that is after the number.
You may simply ignore it, by instance scanf("%*c%c", &operation);

(the rationale is still the same)

nasser (62)

It works thx
But still can't understand scanf("%*c%c",&operation)
and how it efects scanf("%d",&current_floor);

ne555 (10692)

It doesn't affect it, that's the point.

When you use "%s" it means to read an string. Strings in C are null-terminated.
So when you have

Please enter where do u want to go 'u' for Up- 'd' for Down: u

you have the "u\0" string. Two characters, that you intend to write in `operation', that is only one character long.
That causes undefined behaviour, in your case you write over `current_floor'

MiiNiPaa (8886)

You may simply ignore it, by instance scanf("%*c%c", &operation);

Or you can skip leading whitespaces, which is more robust.

1
2

//Note space in format string
scanf(" %c",  &operation);

nasser (62)

ne555: Now I got it thx alot ,in addition I have tryied replaces the lines and it works too
MiiNiPaa:I have tryied your way it woks too
Thx alot guys

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scanf gives me Zero