Using INT_MAX and INT_MIN in C/C++

In this article, we’ll take a look at using INT_MAX and INT_MIN in C/C++.

These are actually useful macros which represent the maximum and minimum integer values.

Let’s take a look at it, using some examples.

Using INT_MAX and INT_MIN

INT_MAX is a macro which represents the maximum integer value. Similarly, INT_MIN represents the minimum integer value.

These macros are defined in the header file <limits.h>, so you must include it.

#include <limits.h>

INT_MAX
INT_MIN

Note that any integer variable must lie between INT_MIN and INT_MAX.

Typically, integers are stored as 4 bytes (32 bits).

This means that in almost all machines, the maximum integer value will be 2^(31) – 1 = +2147483647.

The minimum integer value will be -(2^31) = -2147483648

Let’s verify this, for our machine.

#include <stdio.h>
#include <limits.h>

int main() {
    printf("Maximum Integer Value: %d\n", INT_MAX);
    printf("Minimum Integer Value: %d\n", INT_MIN);
    return 0;
}

Output

Maximum Integer Value: 2147483647
Minimum Integer Value: -2147483648

Indeed, we get what we predict.

Let’s now take another example, to correctly predict any integer overflow or underflow.

#include <stdio.h>
#include <limits.h>

int main() {
    int value = 0;
    while (value >= 0) {
        // Check for overflow
        if (value == INT_MAX) {
            printf("value = %d. Possible overflow!\n", value);
        }
        value ++;
    }
    printf("Now, value = %d\n", value);
    value = 0;
    while (value <= 0) {
        // Check for underflow
        if (value == INT_MIN) {
            printf("value = %d. Possible underflow!\n", value);
        }
        value --;
    }
    printf("Now, value = %d\n", value);
    return 0;
}

Output

value = 2147483647. Possible overflow!
Now, value = -2147483648
value = -2147483648. Possible underflow!
Now, value = 2147483647

While this takes a good few seconds to run, this does indeed do what we expect.

The integer will overflow to INT_MIN, and will underflow to INT_MAX.

This is useful to detect such jumps in the values.

INT_MAX and INT_MIN: Why do we need these macros?

Often, for certain algorithms, it is sometimes necessary to initialize a variable as the lowest/highest value.

The number of bits of the datatype may differ based on the machine.

To make the usage of the maximum/minimum values be consistent, it would be convenient if everyone could use the same macros!

This is exactly why these kinds of macros exist –

• To spare you from remember the actual values
• Have consistent programming patterns across all machines
• Very convenient to use

Hopefully, these reasons may convince you to use such kinds of macros whenever you build your own C/C++ library.