How many strings of five ASCII characters contain the character @ (“at” sign) atleast once? Note: There are 128 different ASCII characters.

Sure, here is the step by step solution:

Step 1: Understand the problem We need to find out how many strings of five ASCII characters contain the "@" sign at least once. There are 128 different ASCII characters.

Step 2: Calculate total number of strings The total number of strings of five ASCII characters is 128^5 because each of the five positions in the string can be any one of the 128 ASCII characters.

Step 3: Calculate number of strings without "@" The number of strings of five ASCII characters that do not contain "@" is 127^5 because each of the five positions in the string can be any one of the 127 ASCII characters (excluding "@").

Step 4: Subtract to find the answer The number of strings of five ASCII characters that contain "@" at least once is the total number of strings minus the number of strings without "@". So, the answer is 128^5 - 127^5.