System Verilog data types

What is an array data type?

The array is the collection of the same data types.

Example:

int array [8] //a collection of 8 int data.

Fixed Size Array

An array with a fixed size of its elements throughout the simulation is known as a fixed-size array.

Example: int array [5]      // it stores 5 elements of type int. (compact declaration)

Code: fixed size array

module tb;
  byte array[3];       //fixed array of byte declaration
  
  initial begin
  
    //assign the values
    array[0]=1;
    array[1]=2;
    array[2]=3;
     
    //print the values of each element
    $display("array[0]=%0d \t array[1]=%0d \t array[2]=%0d", array[0],array[1],array[2]);
  
   
    //you can also print the new array size and element using foreach. 
    foreach(array[i]) begin
      $display("array[%0d]=%0d" ,i,array[i]);
    end
 
  end
      
endmodule

What is the difference between a packed and unpacked array?

Packed:

The size is described before the array’s name so it is an unpacked array.

Bit [7:0] array;        // packed array

Unpacked:

The size is described after the array’s name so it is an unpacked array.

An array of byte, shortint, int are all stored in a single longword, while a longint is stored in two long words. Memory utilization will poor(waste) if we can not use it with proper planning.

Examples:

byte array[4];        // Unpacked array

What are single-dimension and multi-dimension arrays?

In single-dimension array can have only one list of elements, while an array can have multiple lists of elements.

What is a dynamic array?

When you do not know the size of the array until run-time, a better way is to use the dynamic array. It can be modified at run-time. The array must be initialized empty and call the new[] operator for allotment.

Example:

module tb;
  int array[];       //dynamic array declaration
  
  initial begin
    array=new[3];    //size of array 3
  
    //assign the values
    array[0]=1;
    array[1]=2;
    array[2]=3;
    
    //print the size of the array using $size function
    $display("size of the array=%0d ", array.size());
    
    //print the values of each element
    $display("array[0]=%0d \t array[1]=%0d \t array[2]=%0d", array[0],array[1],array[2]);
    
    //modify the size of the array without affecting the previous values.
    array=new[5](array);
  
    //assign the value
    array[3]=4;
    array[4]=5;
    
    //print the new array size and element using foreach loop. 
    foreach(array[i]) begin
      $display("array size= %0d, array[%0d]=%0d" , array.size(),i,array[i]);
    end
    
    //detete all the array elements
    array.delete();
   
  end
      
endmodule

What are single-dimension and multi-dimension arrays?