Char Array and random in 2 two array

guys, I have a question for you. For now, I am trying to learn c language but sometimes I don't know what to do. So, I want to ask you. I hope you can help me. Sorry for my lack of English skills.

First of all, in my homework, I have to do 2 char arrays and with these 2 arrays, I have to make some process(+,-,*). A computer program which it will be preparing has taken 2 number from the user. I think I have to use rand but I don't know it right now.

For example;

first number:9056473829012043267

index-----------18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

array elements 9 0 5 6 4 7 3 8 2 9 0 1 2 0 4 3 2 6 7

second number:6000365738911023

index-----------18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

array elements 6 0 0 0 3 6 5 7 3 8 9 1 1 0 2 3

Total:9062474194750954290

index-----------18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

array elements 9 0 6 2 4 7 4 1 9 4 7 5 0 9 5 4 2 9 0