It is very difficult to comment on the working of this piece of code only since we don’t have the details of your project and the complete code.
What I understood is that, the “convert()” function does the following operations.
-displays a string “output:”
-it extracts the digits from the digit integer “test_final”
-store the digit into two seperate integrs
-convert the integrs into characters, so that they can be displayed on the lcd
-checks whether the number of characters exeeds the number which can be displayed on the first line
-if exeeds go to the next line
-and print “CALIBERATE IT”
Printing an integer on LCD:
You assume a value to test_final variable, say 567.
s=test_final/100; //now s = 5
lcd_data(s+48); // 48 is the ascii value of ‘0’ and 48+5 gives ascii value of ‘5’
//and hence print ‘5’ on LCD
similary it does for 6 and 7.
Have I made it more complex for you?? Take sample value and analyse yourself.