Here's one way to write a program in Python to count the sum of the first 100 numbers:

Copy code
# define a variable to store the sum
sum = 0

# use a for loop to iterate through the numbers from 1 to 100
for i in range(1, 101):
    # add the current number to the sum
    sum += i

# print the final sum
print(sum)

This program uses a for loop to iterate through the numbers from 1 to 100. On each iteration, it adds the current number to the sum variable. At the end of the loop, the sum variable contains the total sum of the first 100 numbers, which is printed to the console.