INT 21h BIOS calls. INT 21h with a value 01 in AH will input a character from the keyboard with echo to the screen. The following is some example code which reads a character with echo and prints the character to the screen. Constant values you wish to store in memory may be placed after your code in memory, but must be considered when determining the number of bytes to write to disk. Not all instructions in the Intel x86 instruction set are the same length, so if you edit your code in memory you cannot expect to always be able to simply substitute one instruction for another.
Palindromes can be of even or odd length.
You should ignore most of it.