How do you count characters in a string in assembly language

Question

I am currently working on a lab for my cs class. Part of the lab is asking for us to make a function that counts the length of a file. The file has a long string inside of it and we need to count the characters in that file. Here is more info on the function

"length_of_file:

#function to find length of data read from file

#arguments: a1=bufferAdress holding file data

#return file length in a0"

" This. asm file contains a function that you will write to find the total amount of data bytes in the csv file. "

"This function is to be written in length_of_file.asm. It accepts as argument in a1 register the buffer address holding file data and returns in a0 the length of the file data in bytes.

From our example involving data.csv, length_of_file(0xffff0000)=119"

Answer 1

A hint: files are terminated by the EOF character, and there is an assembly instruction jne (jump if not equal) that can jump to an instruction. You can create loops in assembly by using the jump instructions, and you can make use of one of the registers as a counter.