43. EQU directive

• EQU directive eliminates hardcoding:

      NUM_OF_STUDENTS  EQU   90
      ..
      mov ecx, NUM_OF_STUDENTS
  

• No reassignment is allowed.

• Only numeric constants are allowed.

• Defining constants has two main advantages:

  1. Improves program readability

  2. Helps in software maintenance.

         mov    ecx, 90 ; HARDCODING is less readable and harder to maintain
     

• Multiple occurrences can be changed from a single place

• The convention is to use all UPPER-CASE LETTERS for names of constants.