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Uninitialized primitive data types in C/C++ Program
In this section we will see when we declare one variable that is un-initialized, which value they hold in C or C++ language. Sometimes we assume that the compiler assigns some value like 0 for int, 0.0 for float etc. But what will be for character datatype? Let us see using implementation and compile using different compilers.
Example (C++)
Let us see the following implementation to get better understanding −
#include <iostream>
using namespace std;
int main() {
char char_var;
float float_var;
int int_var;
double double_var;
long long_var;
cout << char_var << endl;
cout << float_var << endl;
cout << int_var << endl;
cout << double_var << endl;
cout << long_var << endl;
}Output (Compiled in Cpp.sh)
0 0 0 0
Output (Compiled in Online GDB)
5.88054e-39 0 6.95297e-310 0
Output (Local System)
9.73438e-039 4309744 1.15685e-306 -53505136
Now the question comes why C/C++ compiler does not initialize variables with default values? The answer is simple, the overhead of initializing a stack variable is expensive as it hampers the speed of execution, as a result of this these variables can consist of indeterminate values. So, it is treated as good practice to initialize a primitive data type variable before applying it in code.
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