In C all variable names have to be declared before they are used. If you try to use the name of a variable or a function that hasn't been declared you will get an "undeclared identifier" error.

• You issue deals with scoping. To fix your issue you need to declare the variable height before the while lope.

Your code should be the following:

int height;
  do {
    height = Getint();
} while (some condition);

The problem is the semicolon on line 138:

for (int column = 0; column < d - 1; column++);

In C, a semicolon is used to terminate a statement. The body of the for loop (the part in curly braces) is part of the loop statement. If you add a semicolon after the declaration, but before the curly braces, the compiler considers the loop statement to be terminated before the body even starts, producing the for loop has empty body warning.

Now, the loop variable column that you declared in line 138 is only in-scope during the body of the loop. Since you accidentally terminated the loop before giving it a body, column leaves scope immediately after the declaration on line 138. Since you haven't previously declared column in the scope outside of the loop, you get the use of undeclared identifier error.

If you delete the semicolon from the end of line 138 it should fix at least two of those errors; since row is also raising an error, it's likely you have the same problem in an earlier loop declaration. In general, you don't need to use semicolons after for loop declarations or body blocks in C. You only need them in the declaration itself and on the individual statements inside the body. Like this:

for (int i = 0; i < 5; i++)
{
    printf('%i\n', i);
}

Notice there is no semicolon at the end of the loop declaration or after the curly brace that closes the loop body.

Declare #include <stdbool.h> into the header . It will work.Thanks.

You have an extra semicolon after your loop declaration:

for(int i = 0, n = strlen(name); n < i; i++);

this will cause your variables i and n to be undeclared in your expected loop body

The identifier true is not declared by default. To use it, two solutions :

1. Compile in C99 and include <stdbool.h>.
2. Define this identifier by yourself.

However, the infinite loop for (;;) is often considered as better style.

They most often come from forgetting to include the header file that contains the function declaration, for example, this program will give an 'undeclared identifier' error:

Missing header

int main() {
    std::cout << "Hello world!" << std::endl;
    return 0;
}

To fix it, we must include the header:

#include <iostream>
int main() {
    std::cout << "Hello world!" << std::endl;
    return 0;
}

If you wrote the header and included it correctly, the header may contain the wrong include guard.

To read more, see http://msdn.microsoft.com/en-us/library/aa229215(v=vs.60).aspx.

Misspelled variable

Another common source of beginner's error occur when you misspelled a variable:

int main() {
    int aComplicatedName;
    AComplicatedName = 1;  /* mind the uppercase A */
    return 0;
}

Incorrect scope

For example, this code would give an error, because you need to use std::string:

#include <string>

int main() {
    std::string s1 = "Hello"; // Correct.
    string s2 = "world"; // WRONG - would give error.
}

Use before declaration

void f() { g(); }
void g() { }

g has not been declared before its first use. To fix it, either move the definition of g before f:

void g() { }
void f() { g(); }

Or add a declaration of g before f:

void g(); // declaration
void f() { g(); }
void g() { } // definition

stdafx.h not on top (VS-specific)

This is Visual Studio-specific. In VS, you need to add #include "stdafx.h" before any code. Code before it is ignored by the compiler, so if you have this:

#include <iostream>
#include "stdafx.h"

The #include <iostream> would be ignored. You need to move it below:

#include "stdafx.h"
#include <iostream>

Feel free to edit this answer.

It's a scope issue. You're getting compile error because this code is trying to use an undeclared variable, num, to declare the size of a global variable array. num doesn't exist at all at this point:

int candidato[num][4];
int totalVotos[num];

It's a problem later too, because if you do successfully declare the size of the arrays, that size is fixed. There's no way to declare these arrays at the correct size because there's no way to predict how large they will be. All you can do is make a guess of what the maximum size would be, add some extra, just in case, and declare a fixed size. That's going to be either too small, or a waste of memory when it's too big, as well as an invitation to bugs.

Later, num only exists in the function(s) where it is declared. Also, when declared in different functions, each function contains a different version of variables with the same name and they're all unrelated. When I say 'functions', that also includes main().

So, the problem will reappear in main(). The var num is not declared in main, so it doesn't exist when the code tries to use it in the switch statement. It hasn't been declared and no value has been assigned to it.

Remember too, values in variables are passed by copy from main to the functions, or from function to function. That means that the variable in the calling function will remain unchanged, while the called function may or may not change the value in it's local version of the var.

The only way this isn't true is if the var is a global variable. But, well, see below.

Programming tip: This program has numerous global variables. It's a bad practice to use global variables unless absolutely necessary. With so many, I seriously doubt that this many (or perhaps any of them) are necessary. Global variables are an invitation to software bugs, especially when multiple functions are involved. You should try to eliminate using them as globals and set them up as locals.

If this answers your question, please click on the check mark to accept. Let's keep up on forum maintenance. ;-)