To determine an uppercase letter’s decimal value without an ASCII chart, remember the number 65. Write out the entire alphabet in uppercase. Then assign the number 65 to the letter “A. ” From there, assign each subsequent letter with each subsequent number (B = 66, C = 67, etc), ending with Z = 90. Now you have the decimal value for each uppercase letter according to the ASCII chart.
To convert a letter into binary numbers, you’re essentially doing a math equation in reverse. The decimal value for that letter is the “final” answer,” or your starting point. From here, you’re going to work backwards to determine that letter’s binary number in Column 1. To better understand how to do this, let’s do the opposite and convert the binary number “01011010” into a letter to see how this table works. From top to bottom, fill in Column 1 with these numbers: 0 - 1 - 0 - 1 - 1- 0 - 1 - 0. Now multiply each number in Column 1 with the corresponding number in Column 2: 0 x 128 = 0; 1 x 64 = 1; 0 x 32 = 0; etc. Write the answer to each in Column 3 and then add them all up: 0 + 64 + 0 + 16 + 8 + 0 + 2 + 0 = 90. Consult the ASCII chart, and you’ll find that a decimal value of 90 represents the letter “Z. ” Now that you’ve converted a binary number into a letter, working your way backwards through the table to do the opposite should be less daunting. The fact that binary numbers are always either “1” or “0” makes the math easy. Each of the calculated values in Column 3 will always be either “0” or one of the default values that you’ve already written down in Column 2.
To determine a lowercase letter’s decimal value without an ASCII chart, remember the number 97. Write down the alphabet in lowercase. Assign the number 97 to letter “a. ” Then assign each subsequent letter with each subsequent number (b = 98, c = 99, etc), ending with z = 122. Now you have the decimal value for each lowercase letter according to the ASCII chart. [10] X Research source
To convert a letter into binary numbers, you’re essentially doing a math equation in reverse. The decimal value for that letter is the “final” answer,” or your starting point. From here, you’re going to work backwards to determine that letter’s binary number in Column 1. To better understand how to do this, let’s do the opposite and convert the binary number “01111010” into a letter to see how this table works. From top to bottom, fill in Column 1 with these numbers: 0 - 1 - 1 - 1 - 1- 0 - 1 - 0. Now multiply each number in Column 1 with the corresponding number in Column 2: 0 x 128 = 0; 1 x 64 = 1; 1 x 32 = 32; etc. Write the answer to each in Column 3 and then add them all up: 0 + 64 + 32 + 16 + 8 + 0 + 2 + 0 = 122. Consult the ASCII chart, and you’ll find that a decimal value of 122 represents the letter “z. ” Now that you’ve converted a binary number into a letter, working your way backwards through the table to do the opposite should be less daunting. The fact that binary numbers are always either “1” or “0” makes the math easy. Each of the calculated values in Column 3 will always be either “0” or one of the default values that you’ve already written down in Column 2.
