How to print (using cout) a number in binary form?

Use on-the-fly conversion to std::bitset. No temporary variables, no loops, no functions, no macros.

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#include <iostream>
#include <bitset>

int main() {
    int a = -58, b = a>>3, c = -315;

    std::cout << "a = " << std::bitset<8>(a)  << std::endl;
    std::cout << "b = " << std::bitset<8>(b)  << std::endl;
    std::cout << "c = " << std::bitset<16>(c) << std::endl;
}

Prints:

a = 11000110
b = 11111000
c = 1111111011000101

In C++20 you'll be able to use std::format to do this:

unsigned char a = -58;
std::cout << std::format("{:b}", a);

Output:

11000110

In the meantime you can use the {fmt} library, std::format is based on. {fmt} also provides the print function that makes this even easier and more efficient (godbolt):

unsigned char a = -58;
fmt::print("{:b}", a);

Disclaimer: I'm the author of {fmt} and C++20 std::format.

The easiest way is probably to create an std::bitset representing the value, then stream that to cout.

#include <bitset>
...

char a = -58;
std::bitset<8> x(a);
std::cout << x << '\n';

short c = -315;
std::bitset<16> y(c);
std::cout << y << '\n';