Runtime vs. Compile time

Question

What is the difference between run-time and compile-time?

Answer 1

I think of it in terms of errors, and when they can be caught.

Compile time:

string my_value = Console.ReadLine();
int i = my_value;

A string value can't be assigned a variable of type int, so the compiler knows for sure at compile time that this code has a problem

Run time:

string my_value = Console.ReadLine();
int i = int.Parse(my_value);

Here the outcome depends on what string was returned by ReadLine(). Some values can be parsed to an int, others can't. This can only be determined at run time

Answer 2

(edit: the following applies to C# and similar, strongly-typed programming languages. I'm not sure if this helps you).

For example, the following error will be detected by the compiler (at compile time) before you run a program and will result in a compilation error:

int i = "string"; --> error at compile-time

On the other hand, an error like the following can not be detected by the compiler. You will receive an error/exception at run-time (when the program is run).

Hashtable ht = new Hashtable();
ht.Add("key", "string");
// the compiler does not know what is stored in the hashtable
// under the key "key"
int i = (int)ht["key"];  // --> exception at run-time

Answer 3

In simply word difference b/w Compile time & Run time.

compile time:Developer writes the program in .java format & converts in to the Bytecode which is a class file,during this compilation any error occurs can be defined as compile time error.

Run time:The generated .class file is use by the application for its additional functionality & the logic turns out be wrong and throws an error which is a run time error

Answer 4

Hmm, ok well, runtime is used to describe something that occurs when a program is running.

Compile time is used to describe something that occurs when a program is being built (usually, by a compiler).

Answer 5

Run time means something happens when you run the program.

Compile time means something happens when you compile the program.

Answer 6

The major difference between run-time and compile time is:

1. If there are any syntax errors and type checks in your code,then it throws compile time error, where-as run-time:it checks after executing the code. For example:

int a = 1 int b = a/0;

here first line doesn't have a semi-colon at the end---> compile time error after executing the program while performing operation b, result is infinite---> run-time error.

2. Compile time doesn't look for output of functionality provided by your code, whereas run-time does.