Please comment what each line does. Thank you!

Simulate tr Write a C program myTr.c to simulate the features from Unix command tr, which can automatically translate one set of characters to others. The myTr.c takes the option, and a string or two strings as argument. -t can be used to let the characters in first string to be translated into characters in second string. -d can be used to remove the characters in the string from the file. For example, the sample commands to run the program are as below: SmyTr -t abc ABC