C Code: Calculating the Sum of Alternating Series (1-2+3-4...+99)

The code calculates the sum of the alternating series 1-2+3-4+...+99.

The variable 'sn' stores the sum of the series so far, initialized to 0. The variable 'sign' is either 1 or -1, depending on whether the current term should be added or subtracted from the sum.

The loop iterates from i=1 to i<100 (not inclusive of 100), adding or subtracting the current term (i) based on the value of 'sign'. After each iteration, 'sign' is toggled to switch between addition and subtraction.

Finally, the value of 'sn' is printed to the console.

The output of the program is 50, which is the sum of the series.