Please Help!

**Chalmers86** · 01-21-2009

Trouble with program

I’m new to C and seem to be having some problem with my subtracting in “void process” can someone please give me some help?

The problem I have been given to solve is –

“A car hire company calculates the charges for the hire of a car using a standard rate for each mile travelled together with a “wear & tear” surcharge for each complete 1000 miles travelled. Provide a solution which accepts as input the milometer readings at the start and finish of a hire and calculates the total charge for the hire.

Standard rate per mile = £00.42
Surcharge per complete 1000 miles = £10.84”

I’ve attached a picture of the results I get when I run the program also.

Your help would be much appreciated

Chris

Code:

 
//Car hire
//Chris Chalmers
//19/01/2009
 
#include<conio.h>
#include<stdio.h>
 
int miles_before,miles_after;
float rate_per_mile,surcharge,total;
 
void input()
{
    printf("please enter the miles on the clock AFTER rental.");
    scanf("%i",&miles_after);
    printf("Please enter the miles on the clock BEFORE rental.");     
    scanf("%i",&miles_before);
}
 
void process()
{
    total=miles_after - miles_before*0.42;
    if (rate_per_mile>1000);
    {
    total+10.84;
    }
 
}
 
void output()
{
    printf("\nThe total charge for your rental is %.2f",total);
}
 
int main()
{
//clrscr();
input();
process();
output();
getch();
return 0;
}

**MK27** · 01-21-2009

Computer arithmetic generally follows the rules of precedence you hopefully remember from grade school. Try:

Code:

total=(float)(miles_after - miles_before)*0.42f;

Notice (the parantheses). You might also want/need to include the cast (float) since miles_after, miles_before are not floating numbers, and the final f.

**freevryheid** · 01-21-2009

You probably want to change this line in your process() function.

Code:

total+10.84;

If you're adding 10.84 to the total then

Code:

total=total+10.84;

or equivalent

Code:

total+=10.84;

**Chalmers86** · 01-21-2009

Thanks MK27! I think I understand what you mean … I know it as BODMAS (Brackets. Of. Divide. Multiply .Add .Subtract) I completely forgot about the whole concept. Currently doing a HNC at college and I’ve never been great with programming so this probably won’t be the last time I’m on here!

Thanks freevryheid! If you hadn’t mention that my if statement wouldn’t have worked properly either. I would have probably sat at the computer with a blank look on my face for another half an hour!

Thanks very much guys!

**Chalmers86** · 01-22-2009

Like I said yesterday I’m pretty new to C. I’m currently trying to write a program which involves the user entering some characters. I think for the char function you have to set an array? Because it only holds one character at a time? But it doesn’t seem to work when I do it, everything goes all funny after I enter my first line of text.

This is how I set my arrays or attempted to.

Code:

char surname[25],name[25];
int  age,years_worked,retire;

I dunno I think I’m missing something. Like there is more to it than that?

Anyways here is the full program minus my attempt at the arrays

Code:

//Retirement Program
//Chris Chalmers 22/1/2009

#include<stdio.h>
#include<conio.h>

char surname,name;
int  age,years_worked,retire;

void input()

{
     printf("\nPlease enter your christian name.");
     scanf("%c",&name);
     
     printf("\nPlease enter your surname.");
     scanf("%c",&surname);
     
     printf("\nPlease enter your age.");
     scanf("%i",&age);
     
     printf("\nPlease enter the amount of year worked.");
     scanf("%i",&years_worked);
}

void process()

{
 
     retire=(65-years_worked);

}

void output()

{

     printf("Christian Name\n",name);
     printf("Surname\n",surname);
     printf("Age\n",age);
     printf("Years worked\n",years_worked);
     printf("You will retire in\n",retire);

}

int main()
{
input();
process();
output();
getch();
return 0;
}

I dunno I’m finding this so frustrating because I’m beginning to get to grips with the basics and I always forget something so simple!

Anyways once again your help would be much aprreicated.

Chris

**tabstop** · 01-22-2009

% reads a character. Most people have more than one letter in their names.

**Chalmers86** · 01-22-2009

So this instead?

Code:

printf("\nPlease enter your christian name.");
     scanf("c",&name);

Also would I set my arrays at the top like this?

Originally Posted by Chalmers86

Code:

char surname[25],name[25];
int  age,years_worked,retire;

**kcpilot** · 01-22-2009

No, not "c" --- use this --- %s for string which is what the name is (a string).Just replace the "%c" with "%s"

**laserlight** · 01-22-2009

However, a direct replacement of %c with %s will create a buffer overflow loophole. If name and surname are arrays of 25 characters, then they have 24 characters each for the actual name data, hence you would write for name:

Code:

scanf("%24s", name);

Note that the address of name is not taken since it will be implicitly converted to a pointer to the first char to be filled in with the data read.

**Chalmers86** · 01-22-2009

Thanks again guys! That's absolutely brilliant, I feel I am actually really learning stuff as well because you guys are just giving me pointers instead of writing the whole code for me

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