Thread: Problem with my code

Hello,

I just started with programming C. My first task is to code a simple system that ask a question that you can answer with y (yes) or n (no) and goes to the next question. And at the end gives a statement of what can be the problem.

This is my code:

Code:

#include <stdio.h>
void main(void)
{
	char answer_1;
	char answer_2;
	char answer_3;
	char answer_4;
	char answer_5;
	char answer_6;

	printf("Maakt de PC enig geluid?\n");
	scanf("%c",&answer_1);
		if(answer_1=='n') 
		{
			printf("Zit de stekker erin?\n");
			scanf("%c",&answer_2);
					if(answer_2=='n')
					{
						printf("Pffffff......\n");
					}
					if(answer_2=='y')
					{
						printf("Controleer de voeding (zekering kapot?)\n");
					}
		}
		else
		{	
			printf("Is er geen beeld op het scherm te zien?\n");
			scanf("%c",&answer_3);
					if(answer_3=='n')
					{
						printf("Geen 'memory errors' tijdens booten?\n");
						scanf("%c",&answer_4);
							if(answer_4=='n')
							{
								printf("Controleer/vervang SIM geheugenkaarten\n");
							}
							else
							{
								printf("Zijn er meldingen over hard disk errors tijdens het booten?\n");
								scanf("%c",&answer_5);
									if(answer_5=='n')
									{
										printf("Run hardwarediagnoseprogramma. Is alles OK?\n");
										scanf("%c",&answer_6);
											if(answer_6=='n')
											{
												printf("Vervang het foutieve onderdeel.\n");
											}
											else
											{
												printf("Softwareprobleem: herinstalleer windows\n");
											}
									}
									else
									{
										printf("Controleer hard drives en kabels./n");
									}
							}
					}
					else
					{ 
						printf("Controleer videokaart, monitor en bedrading.\n");
					}
		}
}

When i compile it it gives no errors. When i start it it asks the first question and if i answer that with n it gives the second but then it goes to the end of the program in stead of giving the user the change to give new input and scan this. Can anyone tell me what there is wrong?

Thanks for your help!

You want scanf(" %c") -- notice carefully the difference. %c by itself will read in any character, including enter-key (which you're going to type a lot of); the space will cause that to be skipped.

(If you don't want people typing in "yes yes oh yes" then you're going to have to get even more careful with the input.)

Thanks for your help! I changed it and it seems to work fine now. I also tried it with switch function so it would give an error message when people tried to type something different. But I also forgot about the space there.

I got a new task. I should make a ALU simulator in C. It should:
- read the hexadecimal values of 'a' and 'b'
- perform alu operation
- output must look like this example:

32-bit ALU Simulator by Tom

Please enter the values of operands a and b in hex : 01010101 ffffffff
Enter operation code (And, Or, eXor, shift Left, shift Right, +, -) : a
Hexadecimal result: 01010101 a ffffffff = 01010101
Decimal result: 16843009 a 4294967295 = 16843009

This is my code

Code:

#include <stdio.h>
#include <math.h>

void main (void)
{
	unsigned int a;
	unsigned int b;
	char c;
	unsigned int and;
	unsigned int or;
	unsigned int exor;
	unsigned int shiftleft;
	unsigned int shiftright;
	unsigned int add;
	unsigned int subtract;


	printf("32-bit ALU simulator by Tom.\n\n");
	printf("Please enter the values of operands a and b in hex :\n");
	scanf(" %x %x", &a, &b);

	printf("Enter operation code (And, Or, eXor, shift Left, shift Right, +, -) :\n");
	scanf(" %c", &c);

	switch (c)
	{
		case 'a':									//and
			and = a & b;
			printf("Hexadecimal result: %x %c %x = %x", a,c,b,and);
			break;
		case 'o':									//or
			or = a | b;
			printf("Hexadecimal result: %x %c %x = %x", a,c,b,or);
			break;
		case 'x':									//exor
			exor = a ^ b;
			printf("Hexadecimal result: %x %c %x = %x", a,c,b,exor);
			break;
		case 'l':									//shift left
			shiftleft = a << b;
			printf("Hexadecimal result: %x %c %x = %x", a,c,b,shiftleft);
			break;
		case 'r':									//shift right
			shiftright = a >> b;
			printf("Hexadecimal result: %x %c %x = %x", a,c,b,shiftright);
			break;
		case '+':									//+
			add = a + b
			printf("Hexadecimal result: %x %c %x = %x", a,c,b,add);
			break;
		case '-':									//-
			subtract = a - b
			printf("Hexadecimal result: %x %c %x = %x", a,c,b,subtract);
			break;
		default:
			printf("illegal operation code\n");
                        exit();
			break;
	}

	
}

I have some questions:
1. When i perform the and operation the printed result is 1010101. How can I correct that?
2. How can i write the hexadecimal numbers to decimal numbers?
3. The exit() gives an undeclared identifier error. How to solve that?

Thanks in advance for your help!

Thanks for your help. The task said: "Write a simulator for a 32-bit ALU in C. Use unsigned ints for input a,b and result.
For ALU see this Arithmetic logic unit - Wikipedia, the free encyclopedia . My version should take two 32 bit binary words a,b and produces a single 32 bit binary world called result.

new code:

Code:

#include <stdio.h>
#include <math.h>

int main ()
{
	unsigned int a;
	unsigned int b;
	char c;
	unsigned int and;
	unsigned int or;
	unsigned int exor;
	unsigned int shiftleft;
	unsigned int shiftright;
	unsigned int add;
	unsigned int subtract;


	printf("32-bit ALU simulator by Tom Bruls.\n\n");
	printf("Please enter the values of operands a and b in hex :\n");
	scanf(" %x %x", &a, &b);

	printf("Enter operation code (And, Or, eXor, shift Left, shift Right, +, -) :\n");
	scanf(" %c", &c);

	switch (c)
	{
		case 'a':									//and
			and = a & b;
			printf("Hexadecimal result: %x %c %x = %x\n", a,c,b,and);
			printf("Decimal result: %d %c %d = %d\n", a,c,b,and);
			break;
		case 'o':									//or
			or = a | b;
			printf("Hexadecimal result: %x %c %x = %x\n", a,c,b,or);
			printf("Decimal result: %d %c %d = %d\n", a,c,b,or);
			break;
		case 'x':									//exor
			exor = a ^ b;
			printf("Hexadecimal result: %x %c %x = %x", a,c,b,exor);
			printf("Decimal result: %d %c %d = %d\n", a,c,b,exor);
			break;
		case 'l':									//shift left
			shiftleft = a << b;
			printf("Hexadecimal result: %x %c %x = %x\n", a,c,b,shiftleft);
			printf("Decimal result: %d %c %d = %d\n", a,c,b,shiftleft);
			break;
		case 'r':									//shift right
			shiftright = a >> b;
			printf("Hexadecimal result: %x %c %x = %x\n", a,c,b,shiftright);
			printf("Decimal result: %d %c %d = %d\n", a,c,b,shiftright);
			break;
		case '+':									//+
			add = a + b;
			printf("Hexadecimal result: %x %c %x = %x\n", a,c,b,add);
			printf("Decimal result: %d %c %d = %d\n", a,c,b,add);
			break;
		case '-':									//-
			subtract = a - b;
			printf("Hexadecimal result: %x %c %x = %x\n", a,c,b,subtract);
			printf("Decimal result: %d %c %d = %d\n", a,c,b,subtract);
			break;
		default:
			printf("illegal operation code\n");
			return (0);
			break;
	}

	
}

Uninitialized variables are fine, as long as you give them a value before you use them, which you do, so I don't know what MK is complaining about. (Well, I might: the idea is that you just one need one variable called, oh I don't know, result, that you can use in each case rather than one special variable for each operation.)

To get printf to do what you want, why don't you read the manual on printf? (As in, type "man printf" into your terminal, or in that handy little box in the top right-hand corner of your web browser, and read how to make the formatted print statement printf print to your format.)

You had it right without the quotes.

That's what 0xffffffff is, -1. Or did you want to print it as though it was an unsigned int? You should have read your man printf.