Thread: Problems getting printf to print the products of two variables

I am new to coding this is the first programming language I have found that was not overly complicated so I decided I would try to learn this as a first language. I have been doing ok. I have been slowly messing around with tutorials and stuff on the net for a little while. I have decided to make my first serious program (Up till now I have just been making things like hello world programs and what not) I decided to make a small calculator that would calculate the area of a square and as I learned more I could expand upon it to add more features. What I am having problems with is getting printf to print the product of two variables. It does print a number but it does not print the correct number and no matter what numbers you type in it always comes up with the same answer. I will post my code below. if any one could tell me what I am doing wrong I would be very thankful. Any constuctive criticism is also welcome, I am here to learn after all.

Code:

#include <cstdlib>
#include <iostream>  

using namespace std;

int main( int a, int le, int argc, int ar, char *argv[])
{
    ar = (le*2);                                                       /*Declares that ar is the same as le X 2*/
    printf("----------------------------------------------\nWelcome to my simple Area Calculation Program!\n----------------------------------------------\n"); /*prints words to the screen*/
    printf("Lets get started shall we?!\n\n");
    system("PAUSE");                                                   /*Pauses untill the user presses a key*/
    system("CLS");                                                     /*Clears the screen*/
    /*Begining of menu*/
    printf("   Select the shape you wish to calculate the area of\n"); 
    printf("-> 1 - Square\n");
    printf("-> 2 - Rectangle (Comming soon)\n");
    printf("-> 3 - Circle (Comming soon)\n");
    printf("-> ");
    scanf("%d", &a);    /*Asks the user for input, then asigns the input to "a"*/
    /*End of menu*/
    if("&a == 1");      /*Declares that if a is equal to 1 then perform the following*/
    printf("Please enter the Length of one side of the square: ");
    scanf("%d",&le);    /*Asks the user for input, then asigns the input to "le"*/
    printf("\n");
    printf("The area of the square is %d",ar);     /*prints the product of le*le*/
    printf("\n\n");
    system("PAUSE");
    return EXIT_SUCCESS;
}

Hey, thanks for the help. I have corrected a few things but it still does not seem to be working properly. I think I got the standard definition for main fixed and I think I got the headers for C worked out. However I can not figure out what you mean by "Calculate the result after you obtain input" from what I can tell the program is doing just that, or am I missing somthing critical here. I will post the revised code below.

Code:

#include <cstdlib>
#include <stdio.h>

using namespace std;

int main( int argc, char *argv[])
{
int a,le,ar;
    ar = (le*2);                                                       /*Declares that ar is the same as le X 2*/
    printf("----------------------------------------------\nWelcome to my simple Area Calculation Program!\n----------------------------------------------\n"); /*prints words to the screen*/
    printf("Lets get started shall we?!\n\n");
    system("PAUSE");                                                   /*Pauses untill the user presses a key*/
    system("CLS");                                                     /*Clears the screen*/
    /*Begining of menu*/
    printf("   Select the shape you wish to calculate the area of\n"); 
    printf("-> 1 - Square\n");
    printf("-> 2 - Rectangle (Comming soon)\n");
    printf("-> 3 - Circle (Comming soon)\n");
    printf("-> ");
    scanf("%d", &a);    /*Asks the user for input, then asigns the input to "a"*/
    /*End of menu*/
    if("&a == 1");      /*Declares that if a is equal to 1 then perform the following*/
    printf("Please enter the Length of one side of the square: ");
    scanf("%d",&le);    /*Asks the user for input, then asigns the input to "le"*/
    printf("\n");
    printf("The area of the square is %d",ar);     /*prints the product of le*le*/
    printf("\n\n");
    system("PAUSE");
    return EXIT_SUCCESS;
}

Oh I see....so I had to asign a value to ar, after the user asigned a value to le. Thanks for all your help. Program seems to be working much better now.

Ok I have gotten it so that all works properly thanks for your help. I was also wondering if any one could tell me how I could add other options. Currently what my program does is when you enter 1 in the program it lets you calculate the area of a square. What I need to know is how to make it so that when you type in 2 it will let you perform a different task. I have tryed using another if statement but it just uses it as if there where no option and runs it in a straight line. I have also tried using a else if statement but it comes up as gaving an error in it when I try to compile it. Can any one tell me the correct way to use an Else If statement? This is how I have been using it. Can you please try to explain what is wrong with it?

Code:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
int a,le,ar,he;
    printf("----------------------------------------------\nWelcome to my simple Area Calculation Program!\n----------------------------------------------\n");
    system("PAUSE");
    system("CLS");
    printf("   Select the shape you wish to calculate the area of\n"); 
    printf("-> 1 - Square\n");
    printf("-> 2 - Rectangle (Comming soon)\n");
    printf("-> 3 - Circle (Comming soon)\n");
    printf("-> ");
    scanf("%d", &a);
if("&a == 1");
    printf("Please enter the length of one side of the square: ");
    scanf("%d",&le);
    printf("\n");
    ar = (le*le);
    printf("The area of the square is %d",ar);
    printf("\n\n");
    printf("Thank you for using my area calculation program\n\nTo report any errors or to send ideas for future versions\nPlease E-mail me at [email protected] \n");
    system("PAUSE");
else if("&a == 2")
    printf("Please enter the length of the rectangle");
    scanf("%d",&le);
    printf("Please enter the heigth of the rectangle: ");
    scanf("%d",&he);
    ar = (le*he);
    printf("The area of the square is %d",ar);
    return EXIT_SUCCESS;
}

"&a == 1" is a stringliteral.
if used as a boolean it allwais evaluates to true.

Code:

if("&a == 1");

You have put a semicolon after the if statment so that evaluates to if true do nothing.
you want

Code:

if(a == 1) { // start a block
    .... // code that should get executed if a eq. 1
}
else if(a == 1) {
    .... // code that should get executed if a eq.  2
}

BTW the expression

Code:

if(&a == 1)

would mean if the adress of a eq. 1 ....

Kurt

Thanks for the info.....it is working great now. This site is probably the best thing I have found to help me learn :P

If you're going to have more choices (say 3, 4, 5, and 6), you might want to consider using a switch statement instead of multiple if-else if statements. It's a bit easier to read. And if your range of values is small, the performance might be better depending on your compiler.

Here's an example:

Code:

switch (a) {

   case 1:
         /* do area of square here */
      break;
   case 2:
        /*  do area of rectangle here */
      break;
   case 3:
        /* do something else here */
      break;
    case 4:
       /* do something else here */
      break;
    case 5:
        /* do something different here */
      break;
    default:
        /* for all values that come in that you are not specifically
            handling
         */
       break;
}

Ok I will definatly try to figure that switch thing out. If I dont get it I will post on here. Thanks for the tip.

You also might find it more convenient to format long lines like this:

Code:

  printf("----------------------------------------------\n"
         "Welcome to my simple Area Calculation Program!\n"
         "----------------------------------------------\n");

This makes them a lot easier to read in your source.

Ok here is an edited version of my code. I would appreciate any input (good or bad).

Code:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
    int num1,num2,plus,sub,le,ar,he,main,a,mul;
    printf("-----------------------------------------\n"
           "Welcome to my simple Calculation Program!\n"
           "-----------------------------------------\n"
           "(c) copyright 2005 James L. Curtis\n"
           "-----------------------------------------\n");
    system("PAUSE");
    system("CLS");
    printf("   Main Menu \n"); 
    printf("-> 1 - Addition\n");
    printf("-> 2 - Subtraction\n");
    printf("-> 3 - Multiplication(coming soon)\n");
    printf("-> 4 - Area Calculation\n");
    printf("-> ");
    scanf("%d", &main);
   switch (main) {

   case 1:
     printf("Please enter a number ");
     scanf("%d",&num1);
     printf("Please enter another number ");
     scanf("%d",&num2);
     plus = (num1+num2);
     printf("Your answer is %d\n\n",plus);
      break;
   case 2:
     printf("Please enter a number ");
     scanf("%d",&num1);
     printf("Enter the ammount you wish to subtract from the first number ");
     scanf("%d",&num2);
     sub = (num1-num2);
     printf("Your answer is %d\n\n",sub);    
      break;
   case 3:
     printf("Please enter a number ");
     scanf("%d",&num1);
     printf("Enter the ammount you wish to multiply the first by ");
     scanf("%d",&num2);
     mul = (num1*num2);
     printf("Your answer is %d\n\n",mul);    
      break;
    case 4:
     printf("   Select the shape you wish to calculate the area of\n"); 
     printf("-> 1 - Square\n");
     printf("-> 2 - Rectangle\n");
     printf("-> 3 - Circle (Comming soon)\n");
     printf("-> ");
     scanf("%d", &a);
    if(a == 1){
     printf("Please enter the length of one side of the square: ");
     scanf("%d",&le);
     printf("\n");
     ar = (le*le);
     printf("The area of the square is %d",ar);
     printf("\n\n");
}
else if(a == 2){
    printf("Please enter the length of the rectangle: ");
    scanf("%d",&le);
    printf("Please enter the heigth of the rectangle: ");
    scanf("%d",&he);
    ar = (le*he);
    printf("The area of the square is %d",ar);
    printf("\n\n");
    }
      break;
}
  printf("Thank you for using Curtis Calculator v1.2\n\nTo report any errors or to send ideas for future versions\n"
          "Please E-mail me at [email protected] \n\n");
  system("PAUSE");	
  return 0;
}

ummm
well how else would u pause your prgram
or clear the screen?
and u mean u change the second one right

It is not a good idea to use two similar symbols like this:
Code:
int main(int argc, char *argv[])
{
int num1,num2,plus,sub,le,ar,he,main,a,mul;Consistent indentation is a plus.

Originally Posted by LoRdHSV1991

well how else would u pause your prgram.

I would not do that. Pausing a console-program makes it useless for input redirection.

or clear the screen?

A console program should not assume that there is a screen at all. stdout could as well be a printer. ( how to clear that )
Kurt