Code executes a line that should be conditional

Question

I am doing a job for college at C++ and, when performing an if/Else for a value of totalf equal to or different from 0, it is not obeyed. How do I exit display only a certain printf of correct condition?

Follow the exit:

Follows the code:

 #include <stdio.h>

 int main() {

       int filial;
       float v1, v2, v3, totalf;

       printf("\ndigite o numero da filial: ");
       scanf("%d", &filial);

       printf("Digite o valor do 1 mes de vendas: ");
       scanf("%f", &v1);

       printf("Digite o valor do 2 mes de vendas: ");
       scanf("%f", &v2);

       printf("Digite o valor do 3 mes de vendas: ");
       scanf("%f", &v3);

       totalf = v1 + v2 + v3;

           if(totalf != 0)
       printf("\no valor total desta filial sera de: %f", totalf);
           else(total == 0);
       printf("\nO valor nao podera ser exibido, favor digitar um valor diferente de 0");

       return 0;

    }

^{Image of code and output}

Answer 1

There was a ; where I shouldn’t be finishing the else, then this clause of if did nothing and the next line performed unconditionally. This is the main error that does what occurred

In addition there is a condition in the else, this is not necessary in this case and in the form realized nor can it be so, or leaves without condition or makes a else if (when fit, not in this case). So my recommendation is always to use if or else from a row, always put on the same parole line as I did in the code below. Or else use keys always. It would not solve this problem and nor would it be avoided, but it gets an easier look.

But there’s also a problem that’s harder to understand that it’s the type of data used. A type float is not accurate and should not be used for comparison that requires it as it is doing. That is, it should never be used as monetary value. Especially equality or difference can give false negatives because of inaccuracy.

I minimized the problem by checking if it is bigger, but it can still give some error situation, unlikely, but it can. The right thing is not to use this given tip ode. See more in What is the correct way to use the float, double and decimal types?.

In this case the problem is not the if rather the type of data. And the if is not a function, so it has no parameters, I think it is important to make these things clear.

 #include <stdio.h>

 int main() {
    int filial;
    float v1, v2, v3;
    printf("\ndigite o numero da filial: ");
    scanf("%d", &filial);
    printf("Digite o valor do 1 mes de vendas: ");
    scanf("%f", &v1);
    printf("Digite o valor do 2 mes de vendas: ");
    scanf("%f", &v2);
    printf("Digite o valor do 3 mes de vendas: ");
    scanf("%f", &v3);
    float totalf = v1 + v2 + v3;
    if (totalf > 0) printf("\no valor total desta filial sera de: %f", totalf);
    else printf("\nO valor nao podera ser exibido, favor digitar um valor diferente de 0");
}

Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.

As already said should avoid Devc++, although your problem has nothing to do with it, and should program C++ in C++, is using C code in C++. Choose which of the two will program, are different languages, although C++ understands C code.

Answer 2

You don’t need to put parameters in Else, see an example where it would make sense to use more than one if and how it would be done:

if(a>5){
   printf("a é maior que 5);
} else if (a < 5){
   printf("a é menor a 5);
} else {
   printf("a é igual a 5);
}

Note that Else is the default condition if none of the above conditions work.

Answer 3

Your if and is correct, but the else it does not receive any parameter or boolean expression, as it is a consequence of if, where the literal translation would be:

if totalf is non-zero print XXXX, if not print YYYYY

Remove the boleana expression of else and your program should work normally.

Answer 4

There are 2 types of programming errors, which are:

• compilation errors
• errors of execution

About the Compilation Errors

They occur when the program we write does not obey the language rules. This type of error is usually easy to detect. The most frequent ones are:

• Forget a semicolon
• Forget to close a key
• Forget to close the quotation marks on a printf or scanf
• Forget to close a comment
• Forget declaration of variables
• Misspelling a word (e.g.: studio.h instead of stdio.h)

About the Errors of Execution

They are more delicate, imperceptible. The program compiles normally without errors, but when running it does not do what we expect it to do. In computer jargon, we call this bug type by bugs.

Many programming beginners are frustrated when they fail to detect the bugs. With experience, you will see that you start to detect them quickly. The important thing is not to panic.

To detect a bug, should try to isolate the error. This can be done using printf in the middle of the code to see what the program is doing step by step. Alternatively, there are special programs called debuggers that allow you to run the program step by step and see the contents of the variables of the program.

Below are some of the bugs classics occurring in C. They are classic because there is no programmer for C who have never made them. I am sure that sooner or later all of you will also make (or have already made) these mistakes, which are:

• Forget to initialize variables
• Forget the & (commercial) in scanf
• Do not put the flags correct (%d,%c,%f,...) in the printf or scanf
• Utilise = instead of ==
• Infinite cycle
• Semicolon in the wrong place
• Do not group instructions when a composite instruction is desired

Your code has some of these problems, so let’s review the same now to make the corrections...

First Problem (Forgot to initialize variables):

int filial;
float v1, v2, v3, totalf;

Correction:

int filial = 0;
float v1 = 0.0, v2 = 0.0, v3 = 0.0, totalf = 0.0;

Second Problem (Do not group instructions when you want a compound instruction and do not insert logical conditions in the else):

  if(totalf != 0)
printf("\no valor total desta filial sera de: %f", totalf);
  else(total == 0)
printf("\nO valor nao podera ser exibido, favor digitar um valor diferente de 0");

Correction (Correctly identify the printf and remove the expression (total == 0) of else:

if(totalf != 0)
   printf("\no valor total desta filial sera de: %f", totalf);
else
   printf("\nO valor nao podera ser exibido, favor digitar um valor diferente de 0");

Or (Close Code Block with Keys):

 if(totalf != 0) {
    printf("\no valor total desta filial sera de: %f", totalf);
 } else {
    printf("\nO valor nao podera ser exibido, favor digitar um valor diferente de 0");
 }

Or (Use Ternary Conditional Operator):

(totalf != 0) ? printf("\no valor total desta filial sera de: %f", totalf) : printf("\nO valor nao podera ser exibido, favor digitar um valor diferente de 0");

Answer 5

To facilitate understanding, each time you read the word "Else", translate to "else". In a simple if, as in this case, the condition != 0 has already been tested first, so it is understood that the other logical alternative is the sentence =0, so you do not need to put it inside Else.