Task: Division of Two Numbers

You will solve this exercise starting from the divide.asm file located in the tasks/div/support directory.

In the divide.asm program, the quotient and remainder of two numbers represented as bytes are calculated. Update the area marked with TODO to perform divisions dividend2 / divisor2 (word-type divisor) and dividend3 / divisor3 (dword-type divisor).

Similar to the mul instruction, the registers where the dividend is placed vary depending on the representation size of the divisor. The divisor is passed as an argument to the div mnemonic.

TIP: If the divisor is of type byte (8 bits), the components are arranged as follows:

  • the dividend is placed in the ax register
  • the argument of the div instruction is 8 bits and can be represented by a register or an immediate value
  • the quotient is placed in al
  • the remainder is placed in ah

If the divisor is of type word (16 bits), the components are arranged as follows:

  • the dividend is arranged in the dx:ax pair, meaning its high part is in the dx register, and the low part is in ax
  • the argument of the div instruction is 16 bits and can be represented by a register or an immediate value
  • the quotient is placed in ax
  • the remainder is placed in dx

If the divisor is of type dword (32 bits), the components are arranged as follows:

  • the dividend is arranged in the edx:eax pair, meaning its high part is in the edx register, and the low part is in eax
  • the argument of the div instruction is 32 bits and can be represented by a register or an immediate value
  • the quotient is placed in eax
  • the remainder is placed in edx

TIP: If the program gives you a SIGFPE. Arithmetic exception,” you most likely forgot to initialize the upper part of the dividend (ah, dx, or edx).

Testing

To test the implementation, enter the tests/ directory and run:

make check

In case of a correct solution, you will get an output such as:

test_first_div                   ........................ passed ...  33
test_second_div                  ........................ passed ...  33
test_third_div                   ........................ passed ...  34

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Total:                                                           100/100

If you’re having difficulties solving this exercise, go through this reading material.