Multiply Variable by Another Variable?

Question

I have a program for a C class I need to write. The program asks for a quantity, and I need to multiply that quantity by another variable which the user inputs. Basic calculator script for a c class :)

I have it set up like this,

    int qty; //basic quantity var
float euro, euro_result;

//assign values to my float vars
euro = .6896; //Euro Dollars
    euro_result = euro * qty; // Euro Dollars multiplied by user input qty

//start program for user
printf("Enter a quantity: ");

//alow user to input a quantity
scanf("%d", &qty);

printf("Euro:       %f \n", euro_result);

Why does it not work as expected?

Solution 1

You have multiply the euro with user given quantity qty before entered by the user. It should be as below: //euro_result = euro * qty; // <-- shift this to the position given below

//start program for user
printf("Enter a quantity: ");

//alow user to input a quantity
scanf("%d", &qty);

euro_result = euro * qty; // Euro Dollars multiplied by user input qty

printf("Euro:       %f \n", euro_result);

Thats all.

Solution 2

The bug is that the line

euro_result = euro * qty;

needs to be after qty is read-in

Solution 3

The statements in a C program are executed sequentially, and expressions are not evaluated symbolically. So you need to reorder your statements this way:

int qty;
float euro, euro_result;

euro = .6896; // store constant value in 'euro'

printf("Enter a quantity: ");

scanf("%d", &qty); // store user input in 'qty'

euro_result = euro * qty; // load values from 'euro' and 'qty',
                          // multiply them and store the result
                          // in 'euro_result'

printf("Euro:       %f \n", euro_result);

Solution 4

I suspect you want to calculate euro_result = euro * qty; only after you have gathered the value for qty.

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Comments

[Kiran Kumar]

Just a comment..remember to initialize the variable as you define them. so that it becomes easier to debug. For example, instead of doing int qty; define it as int qty = 0;

[Zach Smith]

Ah! So put it after the user has selected the qty and it should work. DUH! I am so stupid I did not even think of that.

[Feidex]

Don't worry. It's a common beginner's mistake.

[Zach Smith]

a beginner? What gave it away? :)

[Feidex]

It's a common beginner's reaction to think they're stupid :-)

[Zach Smith]

is it ok for me to post my finished code on here to have people critique? if not is there an ideal location on the web? i am always seeking gurus to lend me their five minutes...

[gpilotino]

yep, it's common when you come from lisp