Newbie baffled

Hello everyone! This is my 1st post here, in fact I just stumbled across these forums as I attempted to solve a problem I have come across. I am a novice programmer trying to teach myself C using IvorHorton's Beginning C 3rd ed.

I'm only at the end of chapter 3 and although I've been enjoying things I'm stumped. One of the exercises in Chapter 3 is to write a simple fahrenheit to celsius converter program. I made what I though was a pretty good fist of it but I can't get it to compile using either Visual C++.Net 2003 or Dev C++. Interestingly, both compilers seem to be complaining not necessarily about my code, but about some lines in the #included stdio header file.

Specifically, VC++ reports error C2059: syntax error : 'type' and the offending line it flags up in stdio.h is:

"typedef _W64 unsigned int size_t;"

Does this have anything to do with the fact that my PC is an Athlon64? Is there perhaps updated header fils I should download, or is my code just borked?

Anyway, here's my source code:

Code:

/**************************************
 *                                      *
 * Solution to Exercise 3.1, page 140 *
 * Temperature converter program      *
 * By Steven MacDiarmid. 16/2/05      *
 *                                      *
 ************************************/*
 
 #include <stdio.h>
 #include <stdlib.h>
 
 int main(void)
 {
    int choice;
    double temp = 0.0, fahr = 0.0, celsius = 0.0;
    
    printf("\n*******************************************************");
    printf("\nTemperature Converter\n");
    printf("\n(C) 2005 SGM Systems");
    
    printf("\n\n1. Convert temperature from degrees Celsius to Fahrenheit.");
    printf("\n2. Convert temperature from degrees Fahenheit to Celsius.");
    scanf("%d", &choice);
    
    switch(choice)
    {
        case 1:
            printf("\n\nPlease enter a temperature in Celsius: ");
            scanf("%lf", temp);
            
            fahr = temp * 1.8 + 32.0;
            printf("\n\n%lf degrees F = %lf degrees C", temp, celsius);
            break;
            
        case 2:
            printf("\n\nPlease enter a temperature in Fahrenheit: ");
            scanf("%lf", temp);
            
            celsius = (temp - 32.0) * 5.0 / 9.0;
            printf("\n\n%lf degrees C = %lf degrees F", temp, fahr);
            break;
            
        default:
            printf("\n\nInvalid selection, enter 1 or 2.");
            break;
    }
    
    system("pause");
    
    return 0;
}

I'm sure it's a pretty ham-fisted attempt but given my limited knowledge I think this should compile. If anyone can spot something amiss I'd be very grateful.

Many thanks, Steve

Code:

/**************************************
 *                                      *
 * Solution to Exercise 3.1, page 140 *
 * Temperature converter program      *
 * By Steven MacDiarmid. 16/2/05      *
 *                                      *
 ************************************/*

The error is in your commenting above. The commenting should be terminated by */ not /*

I tryed this program, this program crashes when the user enters any kind of input when the user is prompted to enter the temperature.

someone correct me if im wrong but you have not used anything that resmbles user input.

when you enter a value, temp is always initlaized as 0 and the program cant do that division. so you need to initialize temp to the value the user inputs.

edit: try this change

Code:

	int temp;

and

Code:

scanf("%lf", &temp);

Originally Posted by bithub

Code:

/**************************************
 *                                      *
 * Solution to Exercise 3.1, page 140 *
 * Temperature converter program      *
 * By Steven MacDiarmid. 16/2/05      *
 *                                      *
 ************************************/*

The error is in your commenting above. The commenting should be terminated by */ not /*

How embarrassing! Thanks. Now to get he damn thing to stop crashing! Thanks for all your patience!

Cheerd, Steve

read the above post

Originally Posted by InvariantLoop

edit: try this change

Code:

    int temp;

and

Code:

scanf("%lf", &temp);

Thanks! Reading your comments made me notice I'd left out those pesky "&" signs. It works now, thanks to you and bithub. Thanks a million folks, I'm sure I'll be back to bug you all some more - there's only another 481 pages to go!

Cheers, Steve

PS, here's the final working code if anyone's interested, feel free to criticise and rip to shreds - it's the only way to learn!

Code:

/**************************************
 *                                      *
 * Solution to Exercise 3.1, page 140 *
 * Temperature converter program      *
 * By Steven MacDiarmid. 16/2/05      *
 *                                      *
 **************************************/
 
 #include <stdio.h>
 #include <stdlib.h>
 
 int main(void)
 {
    int choice;
    double temp = 0.0, fahr = 0.0, celsius = 0.0;
    
    printf("\n*******************************************************");
    printf("\nTemperature Converter\n");
    printf("\n(C) 2005 SGM Systems");
    
    printf("\n\n1. Convert temperature from degrees Celsius to Fahrenheit.");
    printf("\n2. Convert temperature from degrees Fahenheit to Celsius.");
    scanf("%d", &choice);
    
    switch(choice)
    {
        case 1:
            printf("\n\nPlease enter a temperature in Celsius: ");
            scanf("%lf", &temp);
            
            fahr = temp * 1.8 + 32.0;
            printf("\n\n%.lf degrees F = %.2lf degrees C\n\n", temp, fahr);
            break;
            
        case 2:
            printf("\n\nPlease enter a temperature in Fahrenheit: ");
            scanf("%lf", &temp);
            
            celsius = ((temp - 32.0) * 5.0) / 9.0;
            printf("\n\n%.lf degrees C = %.2lf degrees F\n\n", temp, celsius);
            break;
            
        default:
            printf("\n\nInvalid selection, enter 1 or 2.");
            break;
    }
    
    system("pause");
    
    return 0;
}

feel free to criticise and rip to shreds

Not bad, and nicely formatted too. The only complaint I have is your use of system. system takes a pointer to a char (if you don't know what this is - nevermind) as a parameter - you can also supply a string literal - just a string of text in quotes. It executes the command you give it as though you were typing it yourself at the command prompt. So there is a "pause" program somwhere in the system folders on your PC. Well what happens if this program isn't there? It could've been deleted or you could be on a different system. It could also have been replaced with something else, which would cause some interesting problems. Refer to the FAQ for some alternatives.

edit: Specifically, here:
http://faq.cprogramming.com/cgi-bin/...&id=1043284385

Originally Posted by sean_mackrory

Not bad, and nicely formatted too. ....

edit: Specifically, here:
http://faq.cprogramming.com/cgi-bin/...&id=1043284385

Thanks for your kind words Sean. I sort of suspected system would be deprecated for being non-portable code. I checked out the link and when I try to implement the C specific solution using getchar() VC++ throws errors about a missing semicolon on the line int ch; (even though there's one there) and about ch being undefined (even though Visual Studio reports ch as "int ch" in the tooltip when I hover my mouse over it. The funny thying is, if I copy and paste the code into a blank program skeleton it compiles fine, but not if I paste into my own code.

Here's where I'm at now:

Code:

/**************************************
 *									  *
 * Solution to Exercise 3.1, page 140 *
 * Temperature converter program	  *
 * By Steven MacDiarmid. 16/2/05      *
 *									  *
 **************************************/
 
 #include <stdio.h>
  
 int main(void)
 {
	int choice;
	double temp = 0.0, fahr = 0.0, celsius = 0.0;
	
	printf("\n*******************************************************");
	printf("\nTemperature Converter\n");
	printf("\n(C) 2005 SGM Systems");
	
	printf("\n\n1. Convert temperature from degrees Celsius to Fahrenheit.");
	printf("\n2. Convert temperature from degrees Fahenheit to Celsius.");
	scanf("%d", &choice);
	
	switch(choice)
	{
		case 1:
			printf("\n\nPlease enter a temperature in Celsius: ");
			scanf("%lf", &temp);
			
			fahr = temp * 1.8 + 32.0;
			printf("\n\n%.lf degrees F = %.2lf degrees C\n\n", temp, fahr);
			break;
			
		case 2:
			printf("\n\nPlease enter a temperature in Fahrenheit: ");
			scanf("%lf", &temp);
			
			celsius = ((temp - 32.0) * 5.0) / 9.0;
			printf("\n\n%.lf degrees C = %.2lf degrees F\n\n", temp, celsius);
			break;
			
		default:
			printf("\n\nInvalid selection, enter 1 or 2.");
			break;
	}
	
	int ch;
	printf ("Press [Enter] to continue");
	while ((ch = getchar()) != '\n' && ch != EOF);
	
	return (0);
}

Thanks for everyone's help. btw, is the last line right - return (0);?
I've never seen brackets placed round the argument to return like that.

> int ch;
If you're getting compile errors, maybe your compiler wants to see this declaration at the top. The newer standard allows what you have.

>is the last line right - return (0);?
I think it's a style issue. I prefer just return 0;.