This program defines four integer variables a, b, c, and d and initializes them to 1, 2, 3, and 4 respectively. It then performs some arithmetic operations on the variables, assigning the result to the variable res. Specifically, it calculates d * b + c - a, which evaluates to 10. It prints res to the console and returns 0 to indicate successful execution. The program demonstrates basic variable declaration and arithmetic operations in C.