Arithmetic Operators

Part of the Fundamentals section of Coddy's Verilog journey — lesson 19 of 90.

Verilog provides basic arithmetic operators: + (addition), - (subtraction), * (multiplication) and / (division).

Code Example:

module arithmetic_demo;
  reg [3:0] a, b;
  reg [7:0] add, sub, mul, div;
  
  initial begin
    a = 4'd9;
    b = 4'd4;
    
    add = a + b;    // 9 + 4 = 13
    sub = a - b;    // 9 - 4 = 5
    mul = a * b;    // 9 * 4 = 36
    div = a / b;    // 9 / 4 = 2
    
    $display("9 + 4 = %d", add);
    $display("9 - 4 = %d", sub);
    $display("9 * 4 = %d", mul);
    $display("9 / 4 = %d", div);
    $finish;
  end
endmodule

Output:

9 + 4 = 13 9 - 4 = 5 9 * 4 = 36 9 / 4 = 2

Important Notes

Division performs integer division (no fractions)
Ensure the result register is wide enough for multiplication results

Challenge

In this challenge, you need to write the correct arithmetic expressions using the operators +, -, * and /.

What to do:

Calculate a + b and store in add
Calculate a - b and store in sub
Calculate a * b and store in mul
Calculate a / b and store in div

Cheat sheet

Verilog arithmetic operators: +, -, *, /

reg [3:0] a, b;
reg [7:0] add, sub, mul, div;

add = a + b;
sub = a - b;
mul = a * b;
div = a / b; // integer division (no fractions)

Note: Ensure the result register is wide enough, especially for multiplication.

Try it yourself

module arithmetic_challenge;
  reg [3:0] a, b;
  reg [7:0] add, sub, mul, div;
  
  initial begin
    a = 4'd12;
    b = 4'd5;
    
    add = ______;   // a + b
    sub = ______;   // a - b
    mul = ______;   // a * b
    div = ______;   // a / b
    
    $display("12 + 5 = %d", add);
    $display("12 - 5 = %d", sub);
    $display("12 * 5 = %d", mul);
    $display("12 / 5 = %d", div);
    $finish;
  end
endmodule